Chap. 4.] Attrattim of Cobe/jcn. 17 



and is exemplified by a variety of eafy experiments. 

 Two leaden balls, having each a fmooth furfacc, if 

 ftrongly compreffed together, will cohere almoft as 

 flrongly as if united by fufion j and even two plates 

 of glafs, if the furfaces are even and dry, will require 

 fome force to feparate them *. By the fame law of 

 nature, the particles of even fluid bodies, in which the 

 attraction is \ neceffarily weaker than in folid fub 

 fiances, indicate a difpofition to unite. 



The drops of dew that appear in the morning on 

 the leaves of plants, affume a globular form, from the 

 mutual attraction between the particles of water. 

 Small portions of quickfilver, when brought near to 

 each other, will run together, and affume the fame 

 globular appearance. Alfo, by the fame law, a veffel 

 may be filled with water, mercury, or any other fluid, 

 above the brim, and the fluid will be obferved to rife, 

 in a convex form. 



To this principle we may very properly refer what 

 is ufually termed capillary attraction. Thus, if a fluid 

 is contained in a veffel not full to the brim, it will al- 

 ways be attracted to the edges of the veffel, and will 

 affume a concave form. Thus, alfo, if two plates of 

 glafs, at a fmall diftance from each other, are im- 

 merfed perpendicularly in water, the fluid will rife 

 above its level between the two plates, and the height 

 to which it rifes will bear a certain proportion to the 

 diftance of the plates. A capillary tube is a tube with 

 an exceedingly fmall bore, and by the fame law which 

 raifes the water between the plates of glafs, a fluid 

 will rife to a confiderable heighth in one of thefe 

 tubes. Both thefe experiments will anfwer equally 

 well in the vacuum of an air pump, which proves that 



* See the late ingenious Dr. Enfield's Inftitutes of Natural Phi- 

 lofophy. 



VOL, I. C the 



