Teneriffe; an astronomer's experiment; or specialities of a residence above the clouds ... Illustrated with Photo-stereographs

Front matter

r ■ ■ I I ■ ■ ■ ■ ■ TENERIFFE, AN ASTRONOMER'S EXPERIMENT. ■ . .MATING POINT OF THE PEAK OF TEHEB1FFE , 12,198 FEET HIGH , SHOWING THE INTERIOR OT THE TERMINAL CRATER OF IHE MOUNTAIN . yesdie/ Si/&st7iv7e*idav» o? Jrsr-^s da/s^/r- 2 "2 - an3r jow&ijA^ by ZtvtU/ Rmut/ AN TENERIFFE, ASTRONOMER'S EXPERIMENT OB, SPECIALITIES OF A EESIDENCE ABOVE THE CLOUDS. BY C. PIAZZI SMYTH, F.R.S.S. L. & E, F.R.A.S. CORRESPONDING MEMBER OP TBE ACADEMIES OP SCIENCE IN MUNICH AND PALERMO; PROFESSOR OP PRACTICAL ASTRONOMT IN THE DNIVERSITT OF EDINBURGH, AND HER MAJESTY 8 ASTRONOMER FOR SCOTLAND. |IIttstral£_ bsify f LONDON: LOVELL REEVE, 5, HENRIETTA STREET, COVENT GARDEN. 1858. {The right of translation is reserved.-] " they (telescopes) cannot be so formed as to take away "that confusion of Bays which arises from the Tremors of the " Atmosphere.

The only Remedy is a most serene and quiet Air, " such as may perhaps be found on the tops of the highest Moun "tains above the grosser Clouds."— Newton's Optics, 1730. TO THE EIGHT HON. SIE CHAELES WOOD, BAET., M.P. .first 3. orb of % gtijmiralfti, WHO, BY HIS ENLIGHTENED PATRONAGE, AT ONCE CONVERTED INTO AN ACTUAL AND SUCCESS. U L PACT, A THEORETICAL IDEA, LONG THOUGHT WELL OF, BUT NEVER PREVIOUSLY CARRIED INTO PRACTICE, THIS BOOK, RECORDING THE CIRCUMSTANCES OP THE EXPERIMENT, gs |UspE.tf ullg 5__its_el>, BY HIS OBEDIENT SERVANT, C. PIAZZI SMYTH, E_IN_ _EGH. December, 1857.

Preface

. TN the month of May, 1856, H. M. Lords Commissioners of the Admiralty, advised by the Astronomer Royal, were pleased to entrust me with a scientific mission to the Peak of Teneriffe. Their Lordships most liberally placed 500.. at my disposal for defraying the necessary expenses; and left me, within bounds of such expenditure, as untrammelled by detailed instructions, as any explorer could desire. No sooner was the authorization known, than numerous and valuable instruments were kindly prof fered by many friends of astronomy; and one of these gentlemeD, Robert Stephenson, M.P., — who had indeed fuUy appreciated the scientific question in 1855, and even asked me to accompany him to the Canaries in that year, — immediately offered the use

PREFACE.

. VIII of his yacht "Titania;" and by this, greatly ensured the prosperity of the undertaking. The object mainly proposed, was, to ascertain how far astronomical observation can be improved, by eliminating the lower third part of the atmosphere. For the accomplishment of this purpose, an equatorial telescope and other apparatus were conveyed in the yacht to Teneriffe, in June and July 1856. There — with the approval of the Spanish authorities, (always ready in that island to favour the pursuits of scientific men of any and every country), the instruments were carried up the volcanic flanks of the mountain, to vertical heights of 8900, and 10,700 feet, and were observed with during two months. On my return from this service in October, I had the honour of presenting to Government a short report on what had been done; following it, in the spring with copies of the original observations, as well as the results deduced.

These were afterwards communicated by authority to, and read before, the Royal Society on the 2nd of June, 1857 ; when they were proposed for printing in the Philosophical Transactions. •

PREFACE.

. IX Being then asked by various friends to prepare some account of the personal experiences under which the said observations were made, as likely to subserve many purposes not reached by the numerical statements of the Memoir, — I have endeavoured, in the following pages, to throw together those parts of my journal which seemed best calculated to bring out the specialities of scientific life, on a high southern mountain. Readers who would study the history, statistics, or physics, of Teneriffe, will find them treated of at length in the several admirable publications by George Glas, Viera, Von Buch, MacGregor, and Barker-Webb cum Berthelot ; here, I have only attempted an humble record of particular labours, with due regard to the objects for which they were undertaken. These objects, I am happy to say, have been so warmly appreciated by my intelligent and scientific publisher, Mr. Lovell Reeve — that although the book threatened to be very costly, by reason of the nature of the illustrative plates, he was prompt in relieving me of every attendant risk and expense.

PREFACE.

. X THE ILLUSTRATIONS. Anxious as myself to put all the actual facts of Nature in the elevated regions that were visited, as completely as possible before the public, Mr. Lovell Reeve has been earnestly at work for some time past, and with the gratuitous and continued assistance of Mr. Glaisher of the Greenwich Observatory, has succeeded in maturing plans for illustrating the letter-press with a series of photo-stereographs, the original negatives of which were taken by myself. This method of book illustration never having been attempted before, may excuse a word on this part of the subject. By its necessary faithfulness, a photograph of any sort must keep a salutary check on the pencil or long-bow of the traveller; but it is not per fect ; it may be tampered with, and may suffer from accidental faults of the material.

These, which might sometimes produce a great alteration of meaning in important parts of a view, may, however, be elimi nated, when, as here, we have two distinct portraits of each object. Correctness is thus secured ; and then if we wish

PREFACE.

. XI to enjoy the effects either of solidity or of distance, effects which are the cynosures of all the great painters, we have only to combine the two photo graphs stereoscopically, and those bewitching qualities are produced. Stereographs have not hitherto been bound up, as plates, in a volume ; yet that will be found a most convenient way of keeping them, not incompatible with the use of the ordinary stereoscope, open below and weU adapted for Mr. Reeve's new form of the instrument, — The Book Stereoscope, — constructed by Messrs. Negretti and Zambra, to fold up in a case like a map, without detriment to its stereoscopic action. I have only further to observe, that while Mr. Reeve has been organizing his application of the manufacturing principle to the printing of photo graphs — Mr. Glaisher has personally superintended the chemical part of the process, in the hands of Mr. Melhuish, of Blackheath, in order to ensure permanence in the pictures so multiplied.

Edinburgh, January 1st, 1858. ERRATA. Page 37, last line,— insert "as " at end of line. „ 54, fifth line,— for " 70," read " 40." „ 64, last line, — for " strong, " read " stony." „ 65, second line,— for "a thousand," read "five hundred." „ 94, last line,—; for "fee," read " feet." ,, 155, sixteenth line,— for " lunologists, " read " selenologists. CONTENTS.

Part I. The Voyage And The Climb

OHAP . PAUE I. SAILING IN THE TRADES 3 II. SANTA CRUZ 24 III. OROTAVA 43 IT» BEGIN THE ASCENT 60 V. ARRIVAL ON GUAJARA 73

Part II. On The Ceatee Of Elevation

I. SECURING THE STATION 93 II. SOUTH-WEST ALARM 110 III. TERM-DAT WORK 124 IV. THE GREAT CRATER 143 V. SOLAR RADIATION 161 VI. WHIRLWINDS AND VISITORS 180 VII. DROUGHT AND LIGHT 195 VIII. END OP GUAJARA CONTEXTS.

Part III. On The Ceatee Of Eeuption

CHAP. PAGE I. SCALING THE CENTRAL CONE 225 II. EARLY EXPERIENCES AT ALTA VISTA . . . 241 III. BRINGING UP THE TELESCOPE 258 IV. BATTLE OP THE CLOUDS . 278 V. SUMMIT OF THE PEAK 294 VI. AUTUMN IN EXCELSIS 317 VII. THE REITERATED QUESTION 333 VIII. THE ICE CAVERN . . . 348 IX LAST OP THE MOUNTAIN 372

Part IV. Lowlands Of Teneeiffe

I. SEASONS AND PLANTS 397 II. DRACŒNA DRACO 410 III. ADIEU LIST OF PHOTO-STEREOGRAPHS. Inserted Described at at PAGE PAGE 1. CULMINATING POINT OF THE PEAK OF TENERIFFE, 12,198 FEET HIGH, SHOWING THE INTERIOR OF the terminal crater of the Mountain . Frontispiece 316 2. VOLCANIC " BLOWING CONE" IN OROTAVA, ON THE NORTHERN COAST OF TENERIFFE 27 ... 55 3. PEAK OF TENERIFFE FROM OROTAVA, ON THE NORTHERN COAST 63 ... 63, 403 4. TENT SCENE ON MOUNT GUAJARA, 8903 FEET HIGH . 103 ... 134 5. SHEEPSHANKS TELESCOPE FIRST ERECTED ON MOUNT GUAJARA, THE PEAK OF TENERIFFE IN THE DISTANCE 131 ... 131 6. CLIFF AND FLOOR OF THE GREAT CRATER — EIGHT MILES IN DIAMETER, AND 7000 FEET ABOVE THE SEA UNDER MOUNT GUAJARA .... 145 ... 144 7. SECOND MATE OF YACHT OBSERVING RADIATION THERMOMETERS ON MOUNT GUAJARA .... 173 ... 172 8.

TRACHYTE BLOCKS ON GUAJARA 193 ... 167 9. MASSES OF LAYA SLAG AT ALTA VISTA . . . . 215 ... 250 10. SPECIMEN OF THE MALPAYS OF BLACK LAVA, NEAR ) I 248, 297, ALTA VISTA ) ( 363 11. CLOSE VIEW OF ALTA VISTA OBSERVING STATION, FROM THE EAST — ALTITUDE 10,702 FEET . . 283 ... LIST OF PHOTO-STEREOGRAPHS. XVIII Inserted Described at at PAGE PAGE 12. ALTA VISTA OBSERVATORY, FROM THE NORTHERN LAVA RIDGE 303 ... 2S5, 325 13. ENTRANCE TO THE ICE CAVERN, IN THE MALPAYS OF THE PEAK OF TENERIFFE, AT THE HEIGHT of 11,040 feet 321 ... 351, 363 14. euphorbia canariensis on the sea-coast of orotava 339 ... 406 15. YOUNG DRAGON-TREES AND DATE PALM IN A CACTUS GARDEN NEAR OROTAVA 357 ... 406, 413 16. YOUNG DRAGON-TREES (dRACŒNA DRACO) NEAR OROTAVA 373 ... 414 17. DRAGON-TREE WALK AT A PALAZZO NEAR OROTAVA 391 ... 414 18.

COCHINEAL GATHERERS AT OROTAVA 405 ... 406, 414 19. THE " GREAT DRAGON-TREE" AT THE VILLA DE ORO- TAVA 419 ... 419 20. TRUNK OF THE QREAT DRAGON-TREE 427 ... 427 MAP. MAP OF THE ISLAND OF TENERIFFE, WITH GEOLOGICAL SECTIONS OF THE PEAK x_ii

Chapter I. Sailing In The Trades

/^vNCE within the parallels of the Trade-wind, every " other natural phenomenon is found to give way before that grand commotion of the atmosphere. Therein does nature constantly seek — according to Lieutenant Maury's happy generalization — to restore to the air that moisture which was forcibly abstracted by the cold of the Polar circle ; in order to be enabled, on passing into the opposite hemisphere, to distribute genial showers. The region of these winds appears eminently one of mechanical energy; for, driven by all the tropical power of the sun, its "cumuloni" clouds are ever hurrying along overhead, while the swell ofthe ocean hastens after them below; growing as it goes, and curling into foam, agitating and suffering agitation in a continually increasing ratio. So we found it on board Mr. Stephenson's good yacht Titania, as she winged her speedy way to B Teneriffe, with her important freight of astronomical instruments, in the latter end of June and beginning of July, 1856.

Her beautifully-formed iron hull bounded over the waves as lightly as a pleasure skiff, and with far greater velocity. But how she did roll ! in manner not disagreeably, — for a delicate digestion was not disturbed, — yet that the quantity was most notable, let twenty measured angles, of 15° to 20° each, per minute, sufficiently testify. This rolling, be it understood, was but an expres sion of the disturbed state of the sea at the time ; and, to a certain extent, would have been a necessary expression for any vessel in the same latitude and longitude ; though each, according to its size and rig, would have a scale of its own. The Titania's scale we came to understand before long ; and found its variations minutely sensitive to all the water changes, which the sailors described technically — as, long roll, cross swell, or head sea.

We had now indeed, at last reached a part of the ocean, where the waves were gradually settliug into a more regular and equable movement. But they ran higher than ever, were crested with foam, and gave the horizon a serrated look. Every now and then too, a billow, greater SHOALS OP MEDUSÆ. 5 than his fellows, rushed by, — in the manner of the giant rejoicing to run his course, — and presently broke in a broad white sheet, like snow sparkling in the sun. On such a surface, and under such circumstances, there was little display of animal life. Animals, as well as men, appear only to nourish with a certain degree of quiet. In the zone of calms between the southern and northern Trades, I had been struck, during former voyages, with the abundant manifestations of organic existence. So now, when every living thing seemed to have vanished from the face of the ocean, — we remembered that it was on the 3rd and 4th of July, or immediately before entering the Trade wind region, that five whales had been seen sporting around the yacht, and that we had then passed through an enormous shoal of medusæ.

The least diameter we could assign to the collection was from thirty to forty miles ; and at the rate of one to every ten square feet of surface, — which seemed to be a very moderate estimate, there must have been some 225,000,000 of them, even in the surface stratum. Probably there might well have been so many to furnish food for their giant destroyers ; but for numbers of victims, the whales were infinitely outdone by the medusæ. They were in the form of hollow gelatinous lobes, arranged in groups of five or nine, with an orange vein down the centre of each lobe. They moved slowly by sucking in water at one end of the lobe, and expelling it at the other — a principle of locomotion which, from time to time, inventors have proposed for steam-boats ; but in the medusæ was attended, doubtless, with the means of straining the water of all its dia tomaceous particles.

Examining in the microscope a portion of one of the orange veins, apparently the stomach of the creature, it was found to be extraor dinarily rich in diatomes ; and of the most bizarre forms, as stars, Maltese crosses, embossed circles, semi circles, and spirals. The whole stomach could hardly have contained less than seven hundred thousand; and when we multiply these by the number of lobes, and then by the number of groups, we shall have some idea of the countless millions of diatomes that go to make a feast for the medusæ; some of the softest things in the world thus confounding and devouring the hardest, the flinty-shelled diatomaceæ. When still off the coasts of France and Portugal. O 3 in the earlier part of our voyage, something new or strange, was diversifying every hour. The sailors most SWIMMING CRABS. 7 heartily entering into our wishes, improvised nets, rigged out buckets at the" end of boat-hooks, and with these and other ingenious pieces of machinery, were very successful in fishing up curious things.

Amongst others, they caught certain swimming crabs, with paddles in the place of claws ; paddles — as they appeared, under a high magnifying power, of a rich and tawny yellow colour, with a pattern resembling bunches of hair-brown coral strewed over them, and a blue-grey thread wandering here and there. While we were still speculating on the use to decorative art that might be subserved by this microscopic adorn ment, its fairy painting became confused and nearly obliterated before our eyes, by the death and incipient decomposition of the creature. From the sea we turned to the sky, for in these regions the forms of the clouds were so varied as to be objects of never-ending interest; and the yacht's deck was a famous place for meteorological observation. The delicate cirri, and not much denser cirrostrati, after exhibiting all their phases of beauty, passed at length gradually, and before our eyes, into a peculiar cloud, which may be called cirro-cumulo-stratus.

It is a long, thin, eirrostratus, high in the air, and having a growth of compact little knobs and towers, and, as it were, trees of vapour on its upper surface. Thus garnished, it is a cloud often mistaken for distant land, is eminent for its picturesque qualities, and indicates a strong tendency, or an approach to electric discharge. Some action of this sort was evidently going on in the atmosphere ; and amongst the other clouds, there presently began to form the portentous " lightning cumuli," remarkable, even at mid-day for the flesh tint of their lights, and the steely-blue of their shadows. After sunset, their small-featured, but dense and grandiose masses appeared in dark relief against the western sky. At the same moment in the east, — these electric clouds being the only ones there, able to reflect back any of the faint illumination thrown on them from the opposite quarter, — they seemed to glare out of the darkened heavens, like some pale spectre of momentous size ; and to shake their un earthly light over the waves, from the distant horizon down to the very bows of the yacht.

At midnight followed grand displays of lightning ; awful had we been in the immediate neighbourhood, for the forks were most vivid, and sometimes darted in a group of seven or eight at once. At those instants, so great was the blaze of light, as to reveal LIGHTNING FLASHES. 9 a whole perspective world of cloud-land behind the flashes; sombre mountain ranges of cumulostrati, pierced with dark and long banks of cirri. The instant that the lightning gleam had gone, all this celestial diorama sunk down to a mere murky sky, with a suspicion of being streaked with clouds some what darker than itself. But the interest of the scene was still kept up by the ever-heaving and rest less sea, which, breaking against the sides of the yacht, fell back in luminous foam, scintillating with stellar-looking points ; and once the captain exclaimed, "there's a shark," as some large monster dashed on through the waves by our side, in a perfect path of light.

This used to be the state of things in that pleasant, and then somewhat idle region, to the west of the Iberian Peninsula. One of those days, nearly calm, was studiously spent by a big three-masted vessel on the horizon in forging its way over towards us. By six o'clock p.m. she had got upon our track, though con siderably astern ; and then rounding to, she showed her great broadside like a man-of-war commencing an engagement ; but her intentions were peaceable. The huge Austrian merchant-ship, laden with corn from the Mediterranean, had toilsomely crossed the waters to the little English yacht, solely to ask the longitude ! The sunset was gorgeous that evening ; bathed in golden light, and with massive banks of rich purple cloud, that, continually varying their outline, or rear ing upon one end, and dropping jets of rain, clearly visible in the distance — appeared like huge saurian monsters contending in the air.

A great change came on that night. The sky first grew heavy, then entirely overcast ; a breeze from the N.E. began to spring up ; hour by hour it improved ; and, when the curtain of the next morning was drawn, everything told that the Trades were fairly entered, in the high latitude for them of 39°. Meanwhile the clouds had broken, the old varieties were gone, and a new species, of very uniform character, was arranging its masses in long N.E. and S.W. cumuloni, and yet not cumulous, sort of striæ. The wind continued to freshen until it became a gale ; but always from the same quarter ; and always were the same long lines of cloud above us. They were evidently low, say 3000 to 5000 feet above the sea ; coarse and puffy as to their character and with no difference between their upper and lower outline.

Half fog, half cumulus, they were pulled CLOUD OF THE TRADE-WIND. 11 out into thin long lines — lines interminably long — for day after day we were sailing under them, and never came to their termination. Ever were they observed ranging N.E. and S.W. ; and so parallel, and yet so long, that their zones were seen morning, noon, and night always radiating out of the N.E., and converging into the S.W., points of the horizon. Nor did we cease to distinguish them thus, until they finally coalesced into a general unbroken sheet about the island of Teneriffe. What, then, were these clouds, but a mechanical effect and a sign of the Trade-wind; the cloud material drawn out into streaks by the action of the wind, just as it occasionally pulls into strings, the foaming scum of the waves. Turner gained great feme, in one of his paintings of a storm at sea, by showing such parallel lines of froth along the whole length of a great wave ; but here were lines of aerial foam that stretched from the coast of Portugal, right away down the Atlantic, to the Canarian Archipelago.

This sailing in the Trades — with one unvarying form of cloud overhead, and that not very picturesque; and with a constant, everlasting blow of wind, never rising to a storm, never sinking to a breeze, without lightning, and without rain — is some what monotonous in itself, and makes an uninte resting time to many. But it was an opportunity most precious to me, professionally, for trying some not unimportant experiments in mechanics and astronomy. As thus : — The general question of the angular motions of a ship at sea, while curious to all, has an important bearing with regard to nautical astronomy, the pal ladium of navigation. On shore, the astronomer is always contriving the firmest foundations for his telescopes, and even accuses stone walls of trembling. How then is he straitened on board ship, when his foundation there, does not vary only by two or three tenths of a second in the course of several months, but by the amount of, it may be, 321° (three hundred and twenty-one degrees) in the course of a minute; this being the number of rolls, multiplied by their mean angular value, as actually found on board the Titania by measurement.

Such an amount of movement must prove a com plete bar, and in fact always has, to any sort of observation, but such as can be carried out by Had ley's quadrant — an instrument in one respect inde- GALILEO'S PROBLEM. 13 pendent of a ship's motion. It is excellent so far as it goes, but still leaves many most important phenomena quite to the mercy of the waves — viz., any that require a high magnifying power, or that need a fixity of position in the telescope, and artificial referring-points for horizontality and verti cality. Herein is included such a wide range of subjects, important to science, and useful to the sailor, — that remedies have continually been attempted from the days of Galileo down to our own, but as yet with utter want of success. The fine old Italian fancied that he had discovered an easy method of determining longitudes at sea, by the simple observation of the eclipses of Jupiter's satellites ; and he proceeded to bargain with the King of Spain, then the strongest naval power, for a magnificent reward, in return for so many telescopes to be made by himself.

On shore his tubes proved perfectly equal to their work, that of showing the Jovian satellites clearly and distinctly; but, on a ship's deck, alas! no mortal man could use them. Galileo's difficulty is still unsolved ; an observing chair, or stand, on which a telescope may be placed, is still a desideratum for the sailor. Not a few such machines have been attempted in times past on the principle of a pendulum ; and the inventor of one of them (Nairne), in the days of Captain Cook, was re warded by Government. Prematurely ; as he failed in practice ; and for the reason Sir John Herschel has well pointed out, in the "Admiralty Manual for Scientific Inquiry ;" viz., that " free suspension tends rather to perpetuate than to eliminate disturbances." The dinner-tables on board the yacht, hung from pivots, were on a plan once proposed for observers, and answered wonderfully for mere dining purposes.

Bottles and glasses remained steadily in their places, even when the tables seemed occasionally to swing so low, as to be pointing downwards nearly to the carpet under our feet. But it cannot be too distinctly understood, that keeping a dinner-service from falling, or its liquid contents from outpouring, is a perfectly different thing to preserving a platform truly level, as regards either the horizon or the direction of gravity. The latter is what is needed for astronomical observation ; and that a swinging body does not procure it, even when a glass of water is kept from spillino*, may be powerfully demonstrated, by attaching the said glass to a string held in the hand, and swino-ino it,—not only through large arcs, in imitation of the rolling of a ship,— but round and round, through the SHIP CLINOMETER. 15 whole 3603.

Let this be tried by any one, and no water will be spilt ; the dinner requirement will have been accomplished ; but, oh ! for the astronomical one ; as the surface of the water, during the experiment, will have successively deviated from the horizon through every possible angle. With a clinometer of new construction, first tried during this voyage, we applied measure to the case ; and found that when the deck inclined 18 times per minute, through an average angle of 15°, — the tables in question rolled 42 times in the minute, through about 7°. The tables were heavy, with their hanging weights (several hundred weight), and their pivots were endued with much friction; but still their oscillations, as pendulums, during the rolls of the ship were perfectly sensible. These, sometimes opposing, and sometimes combining therewith, tended greatly to increase the confusion of the movement.

With the barometer, a small weight in lighter gymbals, the vibrating effect was still more prejudicial. Hence, again, the propriety of Sir John Herschel's views, of trying to modify the evils of free, by some what stiff suspension. Yet the evils are thereby only modified, by no means removed ; as every increase in the stiffness of the suspension, in proportion as it checks the oscillations of the table as a pendulum, must communicate the roll of the ship. The only complete and radical cure, then, is to be sought for in somethin<r altogether different from the much-tried pendulum principle. Such means of rectification appear to exist in the force which keeps the axis of the earth in a constant position, as it annually revolves about the sun : viz., the rotation of a heavy body round a free axis.

Models of an apparatus on this plan were shown at the French Exhibition, and are described in the "Transactions of the Boyal Scottish Society of Arts" for the years 1855 and '56. Suffice it now to say, that on July 3 rd, on board the yacht Titania, in lat, 41°. 16'. N., long. 10°. 51'. W., with the rolls ofthe vessel amounting to 25 per minute of 10° each, and the pitches to 27 per minute of 3° each, we tried the largest apparatus of this description yet manu factured. The only available place on deck for the erection of the instrument, was at the vessel's extreme stern, with a look-out over the quarter; just where most up and down motion occurs, and with full effect of rolling. This, however, was well for testing to the uttermost the new principle, which had this feat FREE-REVOLVER STAND. 17 set before it — to enable an observer, without using his hands, to keep a telescope constantly directed on a distant object in spite of the waves.

A sort of observing box had been provided, which, while allowing inser tion of the observer's head and hands, as well as affording a free opening for vision, kept out the rude ness of the wind. But the essence of the means to ensure the all-important steadiness, was a wheel one foot in diameter, eleven pounds in weight, suspended and balanced in gymbal rings; as well as capable of being put into rapid rotation by two trains of wheels, acting on either side of its axis. The captain called up the sailors to drive those wheels. Two strong men at each handle, and the striking together of hundreds of steel and iron teeth many times in a second — as the axles spun round with a velocity almost unprecedented in practical mechanics — soon produced a thrilling sound that called up every one to see what was going on.

They found it of course a most unnautical proceeding. Presently, on the wheels being thrown out of gear, and the gymbal rings undamped, the sound died away, though the revolver went on spinning. Then following with my head the small apparent motions of the eye-piece, I looked in, and had the c satisfaction of finding the horizon of the sea remaining steadily in the field of view. All the rolling of the vessel could avail nothing against the power of the free revolver principle. Adjusting the balance, and then bringing the sea-line on the wire of the telescope, — it actually remained bisected for a considerable length of time ; and the captain, the first and second mates, and many of the crew, were invited to look at it one after another. They saw, and readily confessed the fact, of the useful thing that was now accomplished for the first time at sea ; and throwing their prejudices behind them, they took kindly to the scientific innovation.

The sailors worked with enthusiasm. When ever the driving handle moved in the direction for pulling, they fastened on a rope to it, and clapping their feet against the timbers of the yacht, pulled away as only sailors can pull. They pulled till the multiplying wheels, with their innumerable strikino teeth, shrieked again in their velocity of rotation. Some splendid spins were thus obtained, which o-ave to the table, with nothing visibly supporting it, a firmness like a rock. Touch it, then, incautiously and it resisted like a wild beast ; but press judiciously on THE CRASH. 19 the gymbal rings — and the table was adjusted more accurately than by any tangent screw. The action improved with every increase of speed which we could bring the wheel up to ; and every additional trial saw it revolving a greater number of times in a second.