by the tides until October, when they "Madame la Parqueuse," dressed as are removed for the delicate process of she is in her red flannel knickerbockers detroquage, a process consisting in re- and long boots, sometimes with legs moving each oyster from the tile in bare, and feet in large wooden sandals such a manner as to leave a thin and for more convenient walking on the small fragment of chalk adhering to sand. The men are, as a rule, dressed each shell. It is performed by young in suits of blue cotton, with scarlet women, who use a knife specially man- sash, and head covered with the popular ufactured for the purpose, and re- blue béret. The plage, too, is covered quires the greatest care in execution, with the various implements of the in order that the young and fragile fishery. Piles of tiles are everywhere oyster may not be destroyed. Those to be seen; ambulances, broken and surviving this operation are next passed waiting repair; groups of miscellanethrough two riddles, the meshes of ous articles, as baskets, rakes, spades, which vary in diameter, and being thus wheelbarrows, and wire; bundles of assorted according to size, are placed pignons and stacks of heather, ready in cases called ambulances, frames of for transportation to the park itself. wood two yards by one, covered with a netting of tarred wire, to permit the free circulation of the water. These ambulances are firmly fixed in the sand at the park by means of well-driven piquets, and are the invention of a local culturist. In the ambulance, an oyster will rapidly increase in size, and attain in a few months a diameter of one or two inches. At low-water the ambulances with their contents receive a good watering at the hands of the parqueurs, and this in addition to the covering by the tides twice daily in the natural course. After a sojourn in the ambulance for some months, until sufficiently strong for the purpose, the oysters are scattered abroad like seed in the open claire, where they assume a flat form, and lie for several months until the harvest. But it is necessary to take a boat and engage a man as guide, in order to see many of the most interesting scenes connected with the industry, among them being the gathering of the edible oyster, which is judged eatable by its size, nothing under an inch and a half in diameter being allowed to be sold. This harvest takes place every day except during that period from May to September when the fish are uneatable for the reasons already mentioned. A practice fatal to oyster-culture, and one which almost always results in the destruction of beds by over-fishing, and the removal of the breeding oysternamely, the use of the dredge in fishing is here unknown; and that its use at Arcachon is unnecessary is one chief cause of the success with which the culture is carried on, and the dimenIn order to watch the progress of sions to which the industry has grown. much of the work before described, it Low tide is of course the time for fishis by no means necessary to cross the ing, for then the sea recedes from the channel to the oyster parks lying in claires, leaving only sufficient water to the centre of the Bassin. The plage cover the oysters. The method of proor beach at Arcachon, La Teste, and cedure is for a number of men and the numerous villages on the bay, is at women to form a line at one end of a all times dotted with the parqueurs, claire, and work slowly to the other, busy in the various departments of each carrying a rake, which reveals their profession. Here is a group of the sand-covered oyster, and a wire men and women sorting the edible basket to hold the proceeds of the fishoysters just brought ashore into various ery. On the completion of one claire, sizes and prices; there, another group another is commenced. At the end of at work, cleaning and scraping or whit- a day's work, when the incoming tide ening the tiles, or detaching therefrom will permit its continuance no longer, the young shellfish, each operation in the results are carried ashore, and either its own season. There is no mistaking deposited in the floating warehouses anchored near the beach, or transported by steamboat or railway to their ultimate destination. A large quantity of the finest oysters are transferred to beds in other places, to be fattened, as this process cannot be brought to perfection in the locality. From The Gentleman's Magazine. THE FUEL OF THE SUN. far exceeds all artificial sources of illuTHE dazzling brilliancy of the sun mination. It has been shown experimentally that, compared with a standard A strict watch is kept by day and from the eye, the sun's light is equal in candle placed at a distance of one metre night over the parks, so that no amaquantity to fifteen hundred and seventyteur may try his hand at oyster-gather-five billions of billions of such candles! ing. For this purpose are the numbers (Fifteen hundred and seventy-five folof houseboats which are to be seen dot-lowed by twenty-four ciphers). ting the bay, their white roofs shining in the sun. These contain bed and board for the guardians of the parks. On the Ile des Oiseaux, in the centre of the Bassin, are cabins for the same purpose. Though hardly the place for a successful pearl-fishery, pearls have been found in Arcachon on rare occasions. The intensity of the solar light-or the amount of light per square inch of surface- - is found to be ninety thousand times greater than that of a candle, and one hundred and fifty times as bright as the lime light! The blackest portion of a sun-spot exceeds the lime light in intensity; and even the electric The local museum contains as a curios-arc, when placed between the eye and the sun's disc, appears as a black ity three found together in one shell spot! 1 some years ago. The only other occasion we know of was quite lately, when the writer himself was the lucky finder. Great as is the number of oysters exported from Arcachon annually, it is estimated at not more than two per cent. of those born; and this is comparatively a very large proportion, due to the elaborate manner in which the industry is carried on. It has been estimated that for every oyster brought ashore from the natural beds of Germany, more than one million die. The number to which a mother-oyster gives birth is so large as to be almost incredible, and of these only a very small proportion find their way to the chalkcovered tiles placed for their reception. Many of course are destroyed in the numerous processes through which they pass during the three or four years necessary for such perfection as is attainable in the locality. Altogether, it is an interesting industry, and one in which the picturesque abounds. A pretty sight, the return of the boats on a full tide, after a day's work, when the many sails, white and terra-cotta, dot the clear blue water under a clear blue sky, with a grey line on the horizon, the distant, pine-covered sandhills. What is the fuel of the sun? What is Sir William Thomson has calculated that the quantity of fuel required for each square yard of the solar surface would be no less than thirteen thousand five hundred pounds of coal per hour! equivalent to the work of a steam engine of sixty-three thousand horsepower! This enormous expenditure of fuel would be sufficient to melt a thickness of about forty feet of ice per minute at the sun's surface. Sir John Herschel says, "Supposing a cylinder of ice forty-five miles in diameter to be continually darted into the sun with the velocity of light, and that the water produced by its fusion were continually carried off, the heat now given off constantly by radiation would then be 1 Young's General Astronomy, pp. 212-214. wholly expended in its liquefaction, on | about two hundred and fifty thousand the one hand, so as to leave no radiant miles of the sun's surface, and in this surplus; while, on the other, the actual focus the most refractory substances temperature at its surface would un- platinum, fire-clay, the diamond itself dergo no diminution." He also says -are either instantly melted or dissithat the ordinary expenditure of heat pated in vapor. There can be no doubt by the sun per minute would suffice to that if the sun were to come as near to melt a cylinder of ice one hundred and us as the moon, the solid earth would eighty-four feet in diameter, and in melt like wax." Messrs. Trowbridge length extending from that luminary to and Hutchins consider that in the solar a Centauri ! atmosphere, where carbon is volatilized, the temperature is about equal to that of the voltaic arc. It may be shown that were the sun's mass composed of coal it would all be consumed in about six thousand years. It has been suggested that the solar heat may possibly be maintained by the fall of meteors on its surface. A pound of coal falling on the sun's surface from an infinite distance would develop by concussion six thousand times the heat that would be produced by its combustion. But the enormous quantity of meteors required for the purposeabout thirty-eight hundred pounds per square foot per annum — renders this theory very improbable. If the earth were to fall into the sun it would maintain its heat for a period of less than one hundred years. Jupiter falling into the sun would supply its present expenditure for thirty-two thousand years to come; but, in view of the millions of years indicated by geological records, even this period must be considered as comparatively short. Another objection to this theory is that the quantity of matter required would, in the course of ages, add appreciably to the sun's mass, which would derange the motions of the planetary system. The meteoric theory of the sun's heat must, therefore, be aban As to the actual temperature at the sun's surface, very various estimates have been made by different computers. Secchi supposed it to be about ten million degrees of the Centigrade thermometer and Spörer thirty-seven thousand degrees of the same scale; while M. Pouillet thinks that it lies between 1,461 and 1,761 degrees Centigrade. M. Becquerel, Professor Langley, and Sir William Thomson consider that the temperature of the solar photosphere cannot exceed three thousand degrees Centigrade. According to M. Saint-Claire Deville, the temperature is somewhere about twenty-five hundred to twenty-eight hundred degrees, and this agrees with subsequent experiments by Bunsen and Debray. Sir Robert Ball says that "we shall probably be well within the truth if we state the effective temperature of the sun to be about eighteen thousand degrees Fahrenheit" (The Story of the Heavens, p. 495). Secchi's estimate is probably very excessive, and the smaller determinations nearer the truth. The actual heat of the sun must, however, be very great. Professor Young says: "When heat is concentrated by a burning-glass, the temperature at the focus cannot rise above that of the source of heat, the effect of the lens being simply to move the object at the focus vir-doned. tually towards the sun; so that, if we neglect the loss of heat by transmission by astronomers is that advanced by the through the glass, the temperature at eminent German physicist Helmholtz, the focus should be the same as that of which ascribes the heat of the sun to a point placed at such a distance from the shrinkage of its mass caused by the sun that the solar disc would seem gravitation. It may be shown mathjust as large as the lens itself, viewed ematically that this shrinkage would from its own focus. The most powerful undoubtedly produce the observed relens yet constructed thus virtually trans-sult, and, as gravitation must inevitably ports an object at its focus to within act on the component particles of the The theory now generally accepted sun's mass, it seems quite unnecessary | admit much more than twelve million to look further for a satisfactory the- years as the past duration of the sun's ory. The amount of shrinkage re-history, but, as I have shown in a quired to account for the present solar former paper, this period — immense radiation is so small that the diminu- as it is will not satisfy the demandstion of the sun's apparent diameter of the geologists. To meet this difficould not be detected by the most re- culty Dr. Croll has advanced his "Imfined instruments of measurement. pact Theory," which has been already Sir William Thomson has shown that considered in the paper referred to this shrinkage would amount to only (Gentleman's Magazine, June, 1891). thirty-five metres on the radius per The ancient philosophers thought annum, or one ten-thousandth of its that the sun might possibly be inhablength in two thousand years a quan-ited! Even in modern times this tity quite inappreciable. hypothesis has been seriously considAccording to Helmholtz's theory, the ered. Dr. Elliott in 1787 upheld this sun's heat was originally generated by view, and on his trial at the Old Bailey the collision of two masses, as in Dr. for the murder of Miss Boydell his Croll's theory, but differing from that friends maintained his sanity and theory in the supposition that the quoted as proof of their assertion the bodies approached each other under pages of his book in which this opinion the effects of gravitation alone, and not was expressed. A necessary detail of with any initial velocity. In some Helmholtz's theory is that the sun books it is "paradoxically stated" that must be in a fluid state from its surface the sun is actually becoming hotter to its centre. Were this not so it would owing to condensation; but this is soon grow dark, "as the conducting quite incorrect. As Sir William Thom- power of no known solid would suffice son points out, "cooling and condensa- to maintain the incandescence." The tion go on together." In fact, as the idea of a solid nucleus enclosed in a sun has been gradually losing heat for fiery envelope must, therefore, be abanages past, the amount of heat lost by doned and consigned to the limbo of all radiation must be in excess of that such uncritical theories. gained by shrinkage; and, as this process is probably still in progress, the sun must be actually cooling down. Of course this cooling process is excessively slow so slow, indeed, that one estimate makes the maximum loss not more than one degree Centigrade in seven years. According to Sir William Thomson, if the sun's heat could be maintained by shrinkage until twenty million times the present annual expenditure is radiated away, the sun's diameter would be reduced to one-half what it is at present, and its density would be increased to about the specific gravity of lead. This would probably put a stop to all further shrinkage, through overcrowding of the molecules." 66 Sir William Thomson thus describes the action which would probably take place during the formation of the sun according to the gravitation theory: "Think of two cool solid globes, each of the same mean density as the earth, and of half the sun's diameter, given at rest, or nearly at rest, at a distance asunder equal to twice the earth's distance from the sun, they will fall together and collide in exactly half a year. The collision would last about half an hour, in the course of which they will be transformed into a violently agitated incandescent fluid mass, flying outwards from the line of motion before the collision, and swelling to a bulk several times greater than the sum of the original bulks of the two globes. How far the fluid mass will fly out all Supposing the sun to have been radiating out heat for the past fifteen mil-round from the line of collision it is lion years, the solar radius "must have been four times as great as at present." Sir William Thomson is not disposed to impossible to say. The motion is too complicated to be fully investigated by any known mathematical method. A mathematician with sufficient patience | variables when near a maximum of might, however, approximate to the light indicate a great increase of heat, truth. After a series of oscillations it which may possibly be due either to will subside, probably in the course of the collisions of thousands of meteortwo or three years, into a globular star ites or to solid bodies rendered incanof about the same dimensions, heat, descent by a "violent grazing collision." and brightness as our present sun, but J. ELLARD Gore. different from him in this, that it would have no rotation. From Chambers' Journal. NEGRO COFFEE. "If, however, each had a transverse motion in opposite directions — of 1.82 metres per second, the result would be a globe like our sun, rotating NEGRO or wild coffee is the name in twenty-five days. If the transverse that has been given to fedegozo seeds, velocity be anything more than 0.71 of on account of their being used in westa kilometre they would escape collision, ern tropical Africa and in some of the and would revolve in equal ellipses West India Islands by the natives as a round their centre of inertia in a period substitute for coffee. In some of the of one year, just grazing one another's French African colonies the seeds are surfaces every time they came round to also known as café nègre and café the nearest points of their orbits. If marron. Botanically, the plant producthe initial transverse velocity be less ing the seed is known as Cassia occidenthan, but not much less than, 0.71 of a talis. It grows very freely in most kilometre per second, there will be a tropical countries; in fact, it is a comviolent grazing collision, and two bright mon weed, with a sickly, offensive suns, solid globes bathed in flaming smell, that many planters would fain fluid, will come into existence in the be rid of. The seeds are roasted and course of a few hours, and will com- ground, and the infusion, made in the mence revolving round their common same way as ordinary coffee amazingly centre of inertia in long elliptic orbits resembles the finest Mocha. This fact in a period of little less than a year. is confirmed by Dr. Nicholls of DoTidal interaction between them will minica, who, writing to the director of diminish the eccentricity of their orbits, the Royal Botanic Gardens, Kew, a and, if continued long enough, will few years back, states: "I collected cause them to revolve in circular orbits | some seeds, and directed my cook round their centre of inertia, with a to roast and grind them, so that I distance between their surfaces equal might taste the coffee.' Other matters to 6-44 diameters of each." I was engaging my attention, I forgot the The bearing of the latter portion of circumstance until several days afterSir William Thomson's remarks on the wards, when, one evening, my wife possible origin of binary stars will be inquired how I liked my after-dinner obvious to the reader. The "violent cup of coffee. I turned to her inquirgrazing collisions" in a period of about ingly, when she she laughingly said: a year seem also to suggest a possibleThat is your wild coffee.' explanation of the nature of some of indeed surprised, for the coffee was the variable stars, of which the periods indistinguishable from that made of of several do not differ much from the best Arabian beans, and we in three hundred and sixty-five days. Dominica are celebrated for our good Indeed, this is the theory of variable coffee. Afterwards, some of the seeds, stars advanced by Professor Lockyer in his "Meteoric Hypotheses;" but in this theory the revolving masses are supposed to be swarms of meteorites, and not solid bodies. The bright lines observed in some of the long period roasted and ground, were brought to me, and the aroma was equal to that of the coffee ordinarily used in the island." Dr. Livingstone took some of these seeds to the Mauritius Botanical Gar |