1S47.] 



THE CIVIL ENGINEER AND ARCHITECFS JOURNAL. 



135 



area of the orifice remaining the same, the charge on the centre, being 

 alone exposed to slight errors of measurement, enters into the calcu- 

 lation of the supply or delivery, but as under a radical of the second 

 degree, and the influence of these errors diminishes when the charge 

 increases. 



For this purpose, I caused to be made on the same race or canal, an 

 orifice of 1'4'JG m. (4 ft. 11 in.) in width, the vertical sides of which 

 were 0-16 m. (0-3 inches), and 0-165 ni. (0-5 inelii s; from the sides of 

 walls of the canal, and as the movements or risings of the sluice were 

 very slight, when compared with thfse distances, the contraction 

 might be considered as nearly complete on these sides, as well as on 

 the upper and lower sides. 



The determination of the actual supply or delivery by this orifice, 

 w-ds made, as has been before explained, by means of a small iron 

 sluice, whose greatest opening was 0-300 m. (12 inches). 



The esamination of the results obtained, and above all, their graphic 

 representation, show that the greatest deviations did not amount to 

 more, and were almost always less, than 4\;th of the ordinates of the 

 curve which represents them. And as, for experiments on hydraulic 

 motive powers, such an approximation is quite suthcient, we have 

 been able, in the ulterior calculations of the supply or delivery of 

 water, to adopt the values of the co-efficient of the supply or delivery 

 deduced from this very curve. 



We wish it to be observed that, in our experiments, the charges on 

 tlie summit of the orifices having been comprised between 0-050 m. 

 (2 inches) and 0-180 (7 inches) at farthest, and that this dimension, 

 agreeably to the experiments of Messrs. Poncelet and Les-bros, pro- 

 ducing an influence, atmost, of only ^, the variation of the co-efl5cients 

 has scarcely depended on any thing except the height of the orifices. 



We have therefore been enabled, in accordance with this remark, 

 to seek to compare the values of the co-efficient of the supply or de- 

 livery which we have found, with those which have been determined 

 for equal heights of orificis of 0-20 m. (S inches) in width, by Messrs. 

 Poncelet and Lesbros, and we have thus formed the following table : — 



Nature of the Orifices. 



Values of the co-elBcient of the theoretical 

 supply or delivery for height of orifices 

 of 



0-20 m. 



Orifice of 0-200 ro. wide, 



1-496 m. „ 

 Increase owing to the aug- 

 oientatiuQ of width, 

 Or, 



0-5 92 m. 

 0-6 75 m. 



0-083 m. 

 •100 m. 



8-130 







0-Gll m. 

 0-679 m. 



0068 m. 

 -100 m. 



10-000 



0-05 m. 



0-630 m. 

 0-727 m. 



0097 m. 

 •100 m. 



7-530 



It is seen that the width of the orifice appears to have had a con- 

 siderable influence on the supply or delivery, and that the increase re- 

 iulting from it for this supply or delivery has varied, in the cases in 

 question, frum y j to -^, 



These results prove how necessary it was to verify beforehand the 

 exactness of the formula to be made use of for the measurement of 

 the supply or delivery of water, since differences of this kind might 

 result from it. 



We will moreover observe that these results, giving amounts of 

 supply or delivery much greater than might have been calculated 

 agreeably to the rults generally admitted, the useful effects obtained 

 from the motive powers studied in the experiments of which we have 

 to give an account, will be diminished in the same proportion, and 

 that, in this point of view, our results will be less favourable to them 

 than if we had been content to follow the ordinary rules. 



Evaporation of Water, — A paper was read at the Academy of Sci- 

 ences, Paris, respecting the quaulily of heat annually applied to the eva- 

 puralioD of the water on the surface of the globe, and of the dyoaniic force 

 of the streams of contiueots. BI. Daubree asserts that the evaporation 

 employs a quantity of heat about equal to onethiid of what is received 

 from the sun, or in other words, equal to the melting of a bed of ice of 

 ncitrly 35 feet iu thickness if spread over the globe. The motive force of 

 the streams in Europe is, according to M. Daubr^e, equal to between 

 373,608,974 and 364,678,020 horses working iiicessadtiy during the whole 

 peijud of the year. 



ON M. BRUCHHAUSEN'S NEW THEORY OF THE 



TELLURIC FLUCTUATIONS OF THE SEA. 



By Professor Madlek, of Dorpat. 



Our globe presents an abundance of evidence, that its present con- 

 dition is one which did not exist in times anterior. It is the purport 

 of the present time to establish these facts and their corollaries, his- 

 torically and empirically, and to frame the way for their genitie eluci- 

 dation ; while the purport of the future will be to penetrate into their 

 genesis, and to elucidate, in an incontestible manner, the first causes, 

 ■ — whereby the existing efi'ects and results may be proved and de- 

 monstrated to perfect evidence. We do not intend, by saying so, to 

 discredit all present endeavours to arrive at these first causes of our 

 globe-nature ; — every endeavour in this respect is meritorious. 



This apology we have to premise to our review of M. de Brucli- 

 liausen's (of Luxembourgh) theory of sea-motion, first communicated 

 to the congress of scienltales at Bremen, and subsequently developed 

 in an especial work. Its general features are as follows: — 



1. If masses of ice become fixed on the bottom of the sea, they 

 cause a preponderance of that hemisphere whose pole they form, — 

 and, in consequence of that preponderance, the centre of gravity of 

 the globe must change its place. 



2. Ice masses of this kind are fixed as well at the south as at the 

 north pole, but are not immutable, but increase and decrease alterna- 

 tively. 



3. The fact, especially, that in a cycle of 21,000 years, the poles, 

 have their summer in the periheliuin and apheliura (by wliicli, also a 

 difference in the duration of seasons is given) — causes a disparity in 

 the proportion of evaporation and precipitation, and consequently, a 

 greater increase of the polar ice-masses on that pole which possesses, 

 then, the shorter summer; as well as a decrease of those masses on 

 the opposite pole. 



4. In consequence of the shifting of the centre of gravity, 

 caused by the increase and decrease of these masses, the sea must 

 move to that pole where the bottom-ice is increasing,— flood the land 

 there, and lay dry those on the opposite pole. Thence, so little land 

 exists now on the southern hemisphere, and such breadth of land 

 porects towards the pole on the northern. 



These condensed statements will suffice for testing their plausi- 

 bility. M. de Bruchhausen himself, considers the third argument the 

 weakest, as the observations of Herschel (whose correctness is not 

 disputed by M. B.) have proved, that the sura of the temperature of 

 summer, is not changed by the different position of the Apside line. 

 Still, the distribution of heat over single seasons is, certainly, some- 

 what—albeit, not much— different ; and could, possibly, be the cause 

 of an imperceptible increase of the polar ice. We say possibly, 

 because such a complicated phenomenon demands the most accurate 

 physical inquiry,— which M. Bruchhausen has not made, but endea- 

 vours to prove ills position by induction. 



In this place already, the objection can be raised, that an alternate 

 increase and decrease of ice-masses (at least, as their limits are con- 

 cerned,) takes place every winter and summer, — as, naturally, the 

 winter pole will have more ice than the summer pole. If this differ- 

 ence were of sufficient quantity to act in the way put down by the 

 author, — then, during every summer, we should observe a flowing 

 from the north hemisphere southward ; in winter, one in an oppo- 

 site direction. The elevation of the continents and islands of the 

 temperate and frigid zones, would be different in summer and winter. 

 As, however, such a periodical change of the level of the sea (every 

 year) is, surely, not observed,— then, also, the still lesser difference of 

 aphelic and perihelic summers, is also incapable of producing such 

 astonishing difference of the level of the ocean, which the author 

 estimates at '20,000 feet. This difficulty cannot be obviated, even if 

 the effect of this action be extended to several thousand years. 



The same result will be arrived at by a simple calculation. Let us 

 assume the extent of the polar ice, at an equal distance from the pole, 

 at merely 15°; and as Weddel has sailed up to 74", and Ross even 

 to 78°, south latitude, we might safely consider it eveu as more. Let 

 us further consider the cur\e of its surface (independent of the curve 

 of the globe) as being parabolic : let us take the density of the polar 

 ice at 0-S6; the density of the globe, according to Bailly's latest 

 experiments, at 5-09; and let us express the thickness of the bottom- 

 ice at the pole by a;;— then the shifting of the ceutre of gravity of 

 the globe thereby produced will be : 



- 1 ^ sin 3 15° ;r — ~ a:. 



Whence it results, that for shifting the centre of gravity of the globe 

 only one foot, a mass of ice will be required, which has a thickness ot 



