ATTRACTION*. 18 



Attraction is distinguished into various kinds; 

 but as the causes of eacli are entirely unknown, it 

 is uncertain whether some of them be not different 

 modifications of the same. 



They are, the attraction of cohesion, of gravi- 

 tation, of electricity, of magnetism, and chemical 

 attractions. 



The attraction of cohesion takes place between 

 bodies only, when they are at such very small dis- 

 tances from each other, that they appear to the 

 eye to be in contact. 



If two pieces of lead be scraped clean with a 

 knife, and squeezed together, they will adhere so 

 firmly, that they can scarcely be separated. The 

 same will take place witli planes of glass, or mar- 

 ble, which have been wetted with water. 



It is probably the various degrees of cohesion 

 which different sorts of matter possess, that give 

 their relative degrees of tenacity or hardness. 



The attraction of solids acting on fluids at very 

 small distances constitutes capillary attraction. If 

 a glass tube with a fine bore be held perpen- 

 dicularly in water, it will be perceived that the 

 water will rise in the tube above the level of that 

 in the vessel : and if a number of tubes having 

 bores of different diameters be used together, it 

 will be seen that the water will rise highest in the 

 tube with the smallest bore. Also, if two pieces 

 of glass be kept perpendicularly, and very near to 

 each other in water, the fluid will rise between the 

 glasses. This is owing to the attraction of the 

 glass w r hich acts upon the water. If a woollen 

 thread be hung over the edge of a basin full of 

 water, the water will be attracted by the thread, 

 and made to flow over in drops. 



