158 HYDROSTATICS. SURFACE OF LIQUIDS. 





Prepare a paper mould, and form two leaden cylinders, l cm thic 

 and about l cm< 5 high. Cut a flat face upon each with a pei 

 knife until they are quite bright ; place the faces together, ai 

 bring the whole between the cheeks of the vice. Apply pressn 

 until the length of both cylinders is reduced to about one half 

 the original length ; the faces in contact will adhere with conside 

 able force. 



Fresh-cut surfaces of india-rubber manifest strong adhesion. 

 a tube of black india-rubber be cut with the scissors, both ends a 

 usually closed by the adhesion of the cut edges, and must be opeDt 

 by a slight pressure of the fingers. If, without touching the c 

 surfaces, these be placed in contact again, they will adhere, 

 thus left in contact for some time, the separated parts will 

 joined pretty firmly. 



2. Hydrostatics and Hydrodynamics, or, the Equilibria 

 and Motion of Liquid Bodies. 



19. Surface of Liquids. Transmission of Pressw 

 Pressure in vessels. The molecules of a liquid boe 

 possess very little cohesion, and are displaced from the 

 mutual positions by the smallest force. The sha 

 of a liquid is therefore easily altered; it is general 

 that of the vessel in which it happens to be place 

 Being acted on by gravity, the liquid occupies first t 

 lowest parts of the vessel, which it fills either complete 

 or partially, presenting in any case a free surface whi 

 is a horizontal plane, when the liquid is at rest; tl 

 fact is usually expressed by saying : the surface of si 

 water is level. 



If a small stone or a leaden bullet is suspended b} 

 string from the retort -stand or the frame in fig. I- 

 and allowed to plunge into a basin of water, sligh 

 blackened with ink, the image of the thread produci 

 by reflection at the surface of the liquid will 

 observed to be exactly in a straight line with the thre 1 



