milar manner. 



Xc + ti 



-. --. 



k at 



pi | 



HYDRODYNAMICS. 



could not have been composed more than a few years On Cspillarr 

 before his death in 1662; and he mentions it as if it Att ' OD - 



will be the mean distance of 



the centre of gravity of the solid segment XPN'xpn 

 from the line X -r, estimated in tiie horizontal direction 

 XI'. Bv finding similar distances of the centre of gra- 

 vity o!' all the other wedges or segments, from X x, es- 

 od in the same direction, the sum of all the->e pro- 

 duct* will be the value of b A required. Hence the 



measure of the vessel'* stability ^" X -^ djforan 



angle whose sine is f, is obtained. 



'i ot our readers as wish to prosecute this subject 



e tefeired to the following works : Archime- 



ana! tthuntur in humiio. P. Paul Hoste 



it de la Contraction de* I'aitteaitz, I. yon. 1696. 



.'*. Acad. Par. 1700. Pitot, Themie de la 



.cr de* yaitteaiu, \li-i-.. Acad. Par. 1731. D. 



Bernoulli Comment. Petropol. 1739. vol. x. p. 147; xi. 



p. 100. D'Alerobert's Ettai iitrla resistance de* Flu i Irs, 



and his Opuscule* Mathemnliqutt, torn. 1. Iiouguer's 



Traile de la Manoeuvre de* f'aitseatr. Id. Mrm, Acad. 



Par. 1754, p. 342 5 1753, p. 481 ; 1757, Hist. p. 165. 



Clairant, Mem. Acad. Par. 1760, p. 171. Juan EJ- 



amen Mmrilimo, Madr. 1771- F.ulcr Theorie Complette 



de la, coHtlruction el Manoeuvre de* I'ti'ieamr. This work 



was translated into Englith, and published in 1790, 



Chapman, Traile de la Co*Urttctt* de* I'aitteavx. 



Clairbois Architecture Naval, part ii. Romme I.' Art de 



If Marine, Parii, 1787. Bo*sut Trail r D 11 ydrody- 



nawd(juf, torn. i. chap. xii. xiii. xiv. Atwood 



Trantaetiau, 1796, p. 46 ; and 1796, p. 901. English 



Phil. Mag. vol. i. p. 



CHAP. V. 

 Os C.\piLL*nv AT \-so THE Collision or 



Iv our articles on AoHtssfm andC\rn rvuv A ITBAC- 

 TION, we have already given an acroont of the princi- 

 pal facts relative to the cohesion of fluid*, and 

 of water in capillary tube*. In the present Chapter, 

 we propose to remme the subject, and after tracing the 

 progress of discovery in Urn i branch of phy. 



to lay before our reader* an account of addi- 

 tional experiments which have either been made since 

 the publication of these srlirUs. or which appear to us 

 necessary for completing the view of the tubject which 

 might be expected in the present work. 



The earliest experiments on the ascent of water in 

 eapilliry tubes, appear to hare been first made at Flo- 

 ranee, but we are not acquainted with the name of 

 1 the philosopher who made them, or with the results 

 which he obtained. The editor of the posthumous 

 tracts of Pascal inform* us, that capillary attraction 

 was not known in France when Pascal wrote his post- 

 humous treatise Sur fl'.^nlibre dei Ijye*n, which 



were a fact well known, that the ascent of water in nar- Co( ( 

 row tubes was first discovered by M. Rohault, a cele- riuidi. 



brated Cartesian philosopher, who taught mathematics ^-^^ 



and natural philosophy at Paris. In 1671, Rohault pub- Exp 

 li.hed in *to his Trait f de Physique, which was trans- enu 

 lated into Latin by Dr Clark. This work contains an n ^ 1 

 account of the ordi'nary experiments on capillary attrac- p^ 

 tion, which Rohault ascribes to the unequal pressure of 

 the air within and without the tube. He stiti-j distinct- 

 Iv, that water rises between all bodies which are capa- 

 ble of being wetted with it, whereas it is depressed be- 

 tween substances that are not capable of being wetted. 

 He observed the ascent of water between two plates of 

 glass, and the spherical concavity of the upper fcurlace 

 in capillary spaces ; but he nowhere gives the least hint, 

 that he was the discoverer of these phenomena, t 



In the year 1660, our celebrated countryman, Robert 

 Boyle, published at Oxford his \em Efftcrimentt Phy. 



'ffclianical touching the Spring of the Air, &c. ^ 

 in which he hs* treated of the ascent 'of water in ca- 

 pillary tubes. He ascribes the discovery to some men 

 of science in France, on the authority of a celebra- 

 ted mathematician from whom he received it; and 

 he repeated the experiment with a tube of very small 

 bore, drawn out by means of the blow- pipe. In tl. 

 tube, the water <s said to have sprung instantaneously 

 to the height of /fir inches, to the great surprise of se- 

 veral mathematicians th.it were present. \Vhcn tin- 

 tube was inclined, the water occupied a greater part ni 

 it, and it always rose higher in the tube when the 

 inside of it was wetted before hand. These expe- 

 riments succeeded equally well, when the tubes were 

 placed in an exhausted receiver. Mr Boyle obv 

 also the concavity of the upper surface of the water, llu 

 convexity of the surface of mercury, and its depression 

 in capillary tubes. See the above work, p. 262. 



Dr Hooke seems to have been one of those who was Hooked 

 present at the exhibition of this experiment ; and he is 

 taid to have explained the phenomenon by affinity. In i66o,io6*. 

 a tract published in l'> >. and entitled, " An Attempt 

 for the explication of the Phenomena observable in an 

 experiment published by the Right Hon. Rabert Boyle, 

 in the 35th experiment of his Epistolical Discourse 

 touching the Air, in confirmation of a former conjec- 

 ture made ! I )r HookeJ accounts for the ascent 

 of water in capillary tubes, by the unequal pressure of the 

 atmosphere on the column of fluid within and without 

 the tube. He supposes that there is a greater incongruity 

 between air and glass than between water and glass, and 

 that, on this account, the air i* admitted with more diffi- 

 culty into the tube than the water, the difficulty a). 

 ways increasing as the diameter of the tube diminish- 

 es. This hypothesis Dr Hooke endeavours to sup- 

 port, by the fact which he has determined experimen- 

 tally, that a much greater force is ncreisary to force a 

 bubble of water into a narrow tube than into a wide 

 one ; and be has illustrated it at great length, in 



* Thi. i. Mated U>* ulhr tit, of Fbil. 



t 8c Rohaultii *** >< "10. i M. TO, Tl. 80. Bl. Ac. 



; In IMI. th wcrk mm traailaMd n.lo Uiio. and publUhcd it AnulenUm. (7 M. Bohem, entitled, CWM/M *i t*fUad* Pic 

 MMM wtai L-. . KfftnmtmU fMtui* * //wn^/t Cm HJxrt, BojU. 



| In the jcar 1660." H;> Dr Hook* la hte MftragTar^im, " I printrd little tract, entitled An Aitrmft, ex. ind being unwilling 

 the* to puhli.h thit theory, u tuppminf Iftoiibl be |>rrjuiltcUI to mjr design of natchef. which I wu then procuring patent 

 rnlj hinted the prinnple which I ntppoMd to b* the cni of Ihm pnenonMBB of prfaif^ in the 3li jnft thrreof in the KnglUh 

 i SB* of the Latin rdu.on, AnsC IMS; but referred the further explication thereof till KMM other opportunity." 



I 



