472 



OnCapllUry cohol found by Dr Brewster is almost the same as this, 

 Attraction nal ,, e iy .0178. Benjamin Martin makes the constant 

 Cohesion of q*1tity 18, and Muschenbroek 10. 

 Fluids. M. Gay Lussac obtained the following result for oil 

 of turpentine. 



HYDRODYNAMICS. 



OIL OF TURPENTINE. 

 Diameter of Tube in 



Millimetres. Altitude. 



1.29441 9.95159 



Dr Robison 



Parallel 



plates. 



Newton. 



Experi- 

 ments of 

 Monge. 



The following experiments were made by Dr Robi- 

 son with a tube of a very slender bore. 



Oil of turpentine 1.35 inches. 



Spirits of wine 2.5 



Water 5.5 



Caustic volatile alkali ...... 6.25 



Solution of sal ammoniac .... 8.07 



2. On the Assent of Fluids between Two Plates tfGlas s . 



It appears from the experiments mentioned by New- 

 ton in his Optics, (p. 366. edit. 3d, 1721,) that water 

 rose one inch between two plates of glass, whose dis- 

 tance was -r^g. of an inch, and that water rose to the 

 same height in a capillary tube, the semi-diameter of 

 whose bore was equal to the distance of the plates, 

 which gives .010 as the constant quantity for the glass 

 plates, and .020 as the constant quantity for capillary 

 tubes. 



The following experiments were made by M. Monge, 

 on the rise of water between two plates of glass. The 

 plates of glass were first cleaned with caustic alkali, 

 and carefully washed, and, when separated to different 

 distances, by the interposition of silver wires of diffe- 

 rent thicknesses, they were plunged in the water of the 

 Seine, which had been previously filtered. The diame- 

 ters of the silver wires, from which the distance of the 

 plates was inferred, were obtained by rolling the wire 

 round a tube of glass, and finding the number of thick, 

 nesses which occupied an exact number of lines. By 

 dividing the number of lines by the number of revolu- 

 tions, he obtained the exact diameter of the wire, and 

 consequently the distance of the plates. The follow, 

 ing are the results which he obtained. 



Distance between the 

 plates of glass in parts 

 of a line. 



T*,. or 0.1212 inch 

 & 0.0802 

 ^ O.03571 



Height of the wa- 

 ter above its level, 

 in lines. 



15.5 lines. 

 33.5 



7* 



Constant quan- 

 tity. 



18.786 



26.80 



26.427. 



Messrs Hauy and Tremery likewise observed the 

 height to which water ascended between two parallel Attraction 

 plates of glass placed vertically, at the distance of 1 mil- ,, * nd the 

 limctre, and obtained the following result: 



Distance between the 

 Flutes, Millimetre. 



Density. 

 0.869458 



ments"" . The following are the experiments which were 

 MM Hauy mac ' e at tne desire of La Place, by Messrs Hauy and 

 and Trerae- Tremery : 



*?' Diameter of Height of the Wa- Constant Quantity 



Tube in ter in Millimetres. or Height for a 

 Millimetres. Tube 1 millimetre 



in Diameter. 

 WITH WATER. 



2.0000 6.75 13.500 



1.3333 10.00 13.333 



0.7500 18.50 31.875 



Mean 13.5693 



WITH OIL OF ORANGES. 

 2.0000 3.400 6.8 



1.3333 5.000 6.6667 



0.7500 9.00 6.75 



Height of ascent 

 in Millimetres. 



6.5 



Fluids. 



Constant quantity Expcri- 

 in .Millimetres, ments of 



MM. Hauy 

 and Trtme 



6.5 



M. Gay Lussac measured with great care the rise of Expcri . 

 water between two plates of glass ground perfectly flat, ments of 

 and placed 'exactly parallel to each other. In order to Gay Lussac 

 do this with accuracy, he kept the plates separate n the Hre 

 by four very fine iron wires cut consecutively from of waur 

 the same piece, so as to have their diameters as equal b """, n 

 as possible ; and in order to find the thickness of the p^Tes! 

 wire, he placed a great number of them together, and 

 measured the sum of their diameters. The following 

 was the result of his observations. 



Distance of the Plates 

 of Glass in Millime- 

 tres. 



1.039 



Height of the Water 



to the lowest point 



of the Concavity in 



Millimetres. 



13.574 



Temperature 

 in the Cen- 

 tigrade 

 Scale. 



16 



Incline 

 plates. 



PLATE 

 CCCXV1. 

 Fig. 4. 



The constant quantity is here 14.51, or 0.02251, when 

 reduced to English inches, for a distance of T | 7 th of an 

 inch. 



It is obvious from these experiments, that water as- 

 cends to twice the height in capillary tubes that it does 

 between two plates whose distance is equal to the dia- 

 meter of the tube. 



We have already seen, under CAPILLARY ATTRAC- 

 TION, that if the two plates of glass are inclined to each 

 other at a small angle, the water will rise between them 

 in such a manner that its surface is a hyperbola. Thus, 

 in Plate CCCXVI. Fig. 4. let ABEF, CDEF be the two 

 plates of glass, and DE the surface of the water, then 

 E np D, E m o B will be the surface of the fluid, which 

 Mr Hawksbee found to be hyperbolic, by measuring 

 the ordinates of abscissae of the curves. 



The hyperbolic form of the surface may be deduced 

 from the observed fact, that the altitudes of the fluid in 

 capillary tubes, or between parallel glass plates, are in- 

 versely as the diameters of the tubes, or the distance of 

 the plates. The distance of the plates at m is obviously 

 m n or st, and their distance at o is o p or q r. But m s 

 and o q, being the altitudes of the fluid at m and o, we 

 have ms: o q = o p: mn, but F I : F r = s t or m n : q r, 

 or op. Hence F t : F r = m n : op. But in the Apollo- 

 nian hyperbola, the ordinates are inversely proportion- 

 ed to their respective abscissae, and therefore E m o B is 

 the Apollonian hyperbola. Mr Hawksbee's experiments 

 have already been given in p. 467- 



3. On the Depression of Mercury and Melted Lead in 

 Capillary Tubes. 



If a capillary tube of glass is immersed in mercury, Depressioa 

 or any of the metals in a fluid state, the metallic of mercury, 

 fluid, instead of being elevated like water, stands consi- Lord 

 derably lower in the tube than in its natural surface. 

 The most correct experiments on the depression of mer- v e 

 cury were made by Lord Charles Cavendish. The fol- 

 lowing are the results which he obtained : 



