AND OF THE PHYSICAL SCIENCES. 



75 



. i-^gi 1793. New irruptions of the saa destroyed the dikes and carried away other 



parts of the island of Nordstrand, already so much reduced. 



1803. The sea carried away the ruins of the Priory of Crail in Scotland. 



On the conjectured Buotancy of Bouldeks at great Depths in the 

 Ocean. Travelled Boulder Stones are to be met with in all countries, and in si- 

 tuations where it is extremely difficult to account for their appearance. In addition 

 to the observations which have already appeared in this Journal (see pages 51 and 

 55), we may remark that Lieutenant \V. W. Baddeley, of the Royal Engineers, has 

 communicated to Professor Silliman a curious paper on this interesting subject. He 

 says, " Among the many phenomena which serve to interest and perplex geological 

 students, none are more striking than the formation and position of Boulders, and it 

 is highly probable that no cause, in the first instance, tends more to draw votaries 

 into the labyrinths of this delightful science, than the silent eloquence of these mys- 

 terious masses. We who reside on this new and interesting continent (America), 

 are particularly liable to have our conjectures kept alive respecting them, and it ap- 

 pears to me impossible to pass one of these travelled rocks, without feeling the 

 momentary wish that it possessed the power of speech, and the inchnation to gratify 

 our curiosity concerning them. 



*' I wish to call your attention to the applicabihty of a fact, which, as far as I am 

 aware, has not been pointed out before in any publication, although I doubt not it 

 has occurred to many persons. 



" As long as it was maintained that water was incompressible, an opinion originating 

 in the well known Florentine experiment, an augmentation in the specific gravity of 

 sea water, as the result of pressure, could not be rendered applicable to the inquiry. 

 But the effect of experiments in recent times has been to overthrow the Florentine 

 doctrine in this respect, and to render it probable that the density of water, owing 

 to pressure, increases in a ratio proportionate to its depth. 



•' Now, if this be true, what is the amount of this ratio ? Is it sufficient to give 

 to the waters of the ocean, in their greatest depths, a density equal or superior to 

 that of rock? For if this be conceivable, so is it that Pelagian Boulders are now 

 floating about at great depths in all latitudes ; and if now, then formerly, an admis- 

 sion which would much lessen the difficulty of accounting for their presence in all 

 climes, and in almost all postures ? Thus masses of rock, when once detached from, 

 or reaching the depths of the ocean, might float to the antipodes of the spot where 

 they first commenced their journey, and indeed continue to float until driven by up- 

 ward currents, or other operative causes, upon the sides and summits of submarine 

 hills and mountains, where they might become deposited, in consequence of their 

 superior relative density compared with that of the water, and they are now in, afier 

 having undergone the rounding which they would be likely to meet with in the in- 

 terim from erosion and attrition. 



*' This conjecture (for it is nothing more) will not be considered absurd, I think, 

 when it is recollected that the compressibility of sea water has been proved by Per- 

 kins and others, and is now generally admitted; and that the depth of the ocean, 

 although unknown, must be considerable, some writers making it between two and 

 three miles, while one of them (La Place) considers it to be as high as twenty-five. 

 Bakewell states it to be ' not exceeding ten miles, and more generally admitted not 

 to be over five.' In short, it appears to me that although much is wanted in the 

 way of experiment to determine this interesting question, what is positively known 

 respecting it favors the conjecture now submitted." Lieut. Baddeley proposes the 

 following question, and recommends those who have an opportunity of experimenting 

 to ascertain the relative temperature, density, and saltness of the ocean at various 

 measured depths. 



" Given the specific gravity of a boulder (2.6) at the level of the ocean, what 

 would be its specific gravity in relation to the water it is immediately surrounded by, 

 five miles below the surface, and what its ratio of decrease ?" 



Travelled Stones. — In our last Number, we gave an account of the Travelled 

 Stone of Castle- Stuart. Captain Bayfield has lately laid before the Geological 

 Society an account of the transporting power of the ice peaks framed everv winter 

 in extensive shoals on both sides of the River St Lawrence. These shoals are thickly- 

 strewed with massive boulder stones, round which the ice froze on all sides • and in 

 the Spring, when the river rises from the melting of the snow, the masses of ice, 

 with these stones still frozen to them, naturally float down the river, and frequently 

 carry these boulders to great distances from their native beds, and are left in situation's 

 very remote from any rocks of the same nature. Captain Bayfield also affirms, that 

 icebergs, in which large masses of stone are imbedded in gravel, are annually drifted 

 down the coast of Labrador, through the Straits of Belleisle, and for several hundred 

 miles up the Gulf of St Lawrence. These facts will, in a great measm-e, account 

 for boulders which are found in situations far apart from formations of a similar 

 ■ kind. 



Temperature of the Ii^terior of the Earth.— On Wednesday the I7th 

 August 1835, U. Arago, in delivering a lecture on the theory of the central heat 

 of the earth, related an operation at this time carrying on in Paris, which may be of 

 the highest importance not only to science but to public economy. The municipality 

 have ordered an Artesian well to be pierced near the Barriere des Martyrs; but the 

 men employed, after getting to a depth of 900 feet without finding water, came to a 

 stratum of chalk, so thick, that the undertaking would have been abandoned but for 

 the interference of men of science, who wished it to be contimied, with a view to the 

 elucidation of the above theory. According to observations made by means of a 

 thermometer, no doubt remains as to a fact which hitherto it has not been possible 

 to verify with any degree of precision— namely, that the temperature of the earth 

 rises in regular proportion towards the centre; so that, at the 10th degree from the 

 surface, all known matter must be in a state of fusion. At the point°to which the 

 perforation in question will have reached, U. Arago expects a spring of water will 

 arise of a sufficient degree of heat to warm pubhc establishments,' supply baths, and 

 serve for other purposes. 



METEOROLOGY. 



Equinoctial Rains. — Professor Arago remarks, that navigators occasionally 

 mention rains which fall on their vessels while sailing in equinoctial seas, which led 

 him to think that rain is much more abundant at sea than on land. But this sub- 

 ject still rests merely on conjecture, as it is but seldom that exact measurement are 

 made. Measurements of this kind are not, however, difficult. For example, many 

 measurements were made by Captain Tuckey, in his unfortunate expedition to the 

 River Congo. We know that the discovery ship Bonite will be furnished with a 

 small udometer. Its commander should have it placed on the stern of the vessel, in 

 such a situation, that the rain collected by the sails and cordage cannot drop 

 into it. 



It would add greatly to the interest of those observations, if navigators would de- 

 termine the temperature of the rain, and the height from which it falls. 



To ascertain the temperature of the rain with precision, it is necessary that the 

 mass of the water should be considerable, relatively to the size of the vessel in which 

 it is contained. A metal udometer is unfavorable for this experiment. It would 

 be greatly preferable to have a large pummel of sand, of some tight stuff, for this 

 purpose, very close in its texture; and the water which runs from the under side of 

 it ought to be received by a glass of small dimensions, containing a little thermometer. 

 The only time at which the elevation of the rain clouds can be ascertained is during 

 the storm ; then the number of the seconds which elapse between the appearance of 

 the flash and the time at which the sound reaches the observer, multiplied by 337 

 metres — the degree of rapidity with which the sound is propagated — indicates the 

 lengths of the hypothenuse of a right-angled triangle, whose vertical side is precisely 

 the height required. This height may be calculated if, by the aid of a reflecting in- 

 strument, we estimate the angle formed with the horizon, by the line which, taken 

 from the eye of the observer, terminates in that quarter of the cloud where the light- 

 ning first showed itself. 



If for an instant we suppose, that rain falls on the vessel whose temperature is 

 lower than that which the clouds must possess, judging from their height and the 

 known rapidity of the decrease of atmospheric heat, every person will understand the 

 place which such a fact would occupy in Meteorology. 



If, on the other hand, we imagine that, during a day of hail (for hail does fall in 

 the open sea), the same system of observations had proved that the hailstones were 

 formed in a region where the temperature of the atmosphere was higher than the 

 point at which water congeals, and science would thus be enriched with a valuable 

 result, to which every future theory of hail must necessarily be accommodated. 



Rain in a perfectly Clear Sky. — Some natural phenomena are so extraor- 

 dinary and improbable in their nature, that many who have witnessed these eccentri- 

 cities of nature forbear mentioning them, lest they should be ranked as mere 

 visionaries. The rains of the equinoctial regions may be classed among such phe- 

 nomena. 



In intertropical climates rains have frequently been observed when the atmosphere 

 was pure and serene, with the sky of the most beautiful azure ! The rain-drops on 

 such occasions do not fall thickly, but they are of much larger dimensions than rain- 

 drops in European climates. The fact is certain; we have the assurance of Baron 

 Humboldt, that he observed occurrences of this kind in the interior of countries ; 

 and Captain Beechcy observed ihis phenomenon in the open sea. T\'ith respect to 

 the circumstances on which such a singular precipitation of water can depend, we are 

 entirely ignorant of them. In Europe, in calm and clear weather, during the day, 

 sometimes, very small crystals of ice have been observed to fall gently from the atmo- 

 sphere, their size increasing with every particle of humidity they congeal in their 

 passage towards the earth. Does this approximation put us in the way of obtaining 

 the desired explanation? Have not the large rain-drops of tropical climates been, 

 while in the higher regions of the atmosphere, small particles of ice excessively cold — 

 then in their descent become large pieces of ice by agglomeration; and when lower 

 still, been melted into large drops of water? The object of these conjectures is to 

 exliibit in what point of view the phenomenon may be studied, and to stimulate young 

 travellers in particular, to observe earefully if, during these singular rains, the regions 

 of the atmosphere from which they fall present any traces of halo. If such traces 

 are noticed, however slight they may be, the existence of crystals of ice in the higher 

 regions of the air will be demonstrated. 



In almost every couniry meteorologists are to be met with, but their observations, 

 in too many instances, are made at unsuitable hours,^ and with instruments which are 

 either inaccurate in themselves, or improperly placed. It seems not to be difficult 

 now to deduce the mean temperature of the day from observations made at ary 

 hour : thus a meteorological table, whatever may be the hours noted in it, will be of 

 value by the mere condition that the instruments employed will admit of being com- 

 pared with the student's barometers and thermometers. 



Almost any thermometer will answer the ordinary purposes, but the most usefil 

 barometer which we have seen is Adie's sympiesometer, which is used to determine 

 the pressure of the atmosphere, the altitude of any situation above another, or above 

 the level of the sea. To obtain the altitudes from the common barometer, observa- 

 tion tables are required. The sympiesometer gives the altitudes without the use of 

 tables, and only requires a single process of subtraction and multiplication. 



Direction of the "Winds. — W. C. Redfield, Esq. of New York, makes the fol- 

 lowing observations on this subject: — " It is deserving of notice, that during some 

 of the coldest periods of winter, in this occasionally serene cHmate, the predominatin*' 

 winds blow from the south-western or southern quarters of the horizon. This fact 

 appears to be estabUshed by the annual reports which have been made to the Regents 

 of the University, and it is believed v/ill become obvious in proportion to the accuracy 

 cf our observations. It sufficiently demonstrates, without resorting to other evi- 

 dence, the fallacy of the notion commonly entertained, that winds are genrrally rec- 

 tilinear in their progress, and blow for the most part in right lines over extensive 

 portions of the earth's surface; — an error which appeai-s to remain undisturbed in the 

 minds of some meteorologists*" 



