CAPILLARITY. 



211 



the other separated by a few millimetres, as shown in a 

 horizontal section in fig. 151 B. The liquid will rise 

 between the plates in such a. manner that it will be 

 highest on that side where the plates are nearest together, 

 and the upper surface of the elevated portion of the 

 fluid will form a peculiar curve, as shown in fig. 15U, 

 which gives a side view of the plates with the liquid 

 between them. f A \ }\ \( \ 



FIG. 151 (real size}. 



For these experiments alcohol should be used in preference to 

 water. For dust cannot be prevented from getting inside the 

 tubes, and it will interfere with the moistening of them more 

 if water is used tban if alcohol is employed. Tubes of 2 mm dia- 

 meter may easily be bought ; alcohol will ascend in such a tube to 

 the height of a few millimetres. Narrower tubes may be prepared 

 over the spirit-lamp. A glass tube about 8 or 10 cm long, and 4 or 

 gmm w i(j e> i s heated in the middle, constantly turning it until it has 

 become quite soft ; it is then taken at once away from the flame and 

 rapidly drawn out. In this manner a very narrow tube of from 20 

 to 60 cm is obtained, from which suitable pieces may be cut with the 

 three-cornered file. A piece of 6 or 8 cm may be left at one end of 



p 2 



