]4 0N TIIE ATTRACTION OF SURFACES, 



Description of Fig. 4, plate I, Represents the machine: the part a is si - 



and placer's* miliir to l,,at useJ % gHiziets, which is placed on the outsidt 



machine. of the window. b, is an additional moving piece, which 



presses against the inside of the window frame, and is brought 



nearer to, or removed farther from it, by means of the male 



screw c, and its handle d. 



Fig. 5, Shows the lower part of a window, and the manner 

 in which the moving piece b, including a female screw, acts 

 against the inside of the window frame. 



Fig. 6, Shows a cross bar introduced in place of the moving 



piece last mentioned which bar extends from one window side 



% to the other, ami explains how the machine may be used, 



where any injury might arise from screwing the moving piece 



in the centre of the recess of the window. 



The general improvement consists In the use of a screw on 

 that end of the frame which is within the house, and which 

 keeps the machine steady and firm, instead of the two upright 

 irons, which are put through holes made in the top plank of 

 the machine, in the common mode, and which occasion the 

 machine to be very unsteady in use, and liable to accident. 

 There are two blocks marked rf, c/, in Fig. 4, which may be 

 occasionally put in, or taken out, according as the stone work 

 under the window may require. 



IV. 



Answer to some Observations of Mr. Dispan on the pretended 

 Attraction of Surface between Oil and Water: by J. Car- 



RADORI DE PRATO, M. D*. 



Oil spreads on JlvJL R. Dispan, a celebrated professor of chemistry, imagines 

 attempUopre- tnat tne ph enomenon of the spreading of oil on the surface of 

 serve their le- water arises simply from an effort of libration between two 

 two fluids of bodies of very different specific gravities, as oil and water 

 different gravi- are. " A drop of oil," says he, " falling on still water, is a 

 sphere composed of extremely movable particles, disposed by 

 its difference of gravity to yield the level to the water, and 



• Annales de Chimie, vol. LXII, p." 65, April, 1807. 



consequently 



