Magnetism, Cohesion, Adhesion and Viscosity. 51 9 



to speak more philosophically, to dissolve the film of particles 

 that covers object-glasses and mirrors so rapidly, owing to the 

 affinity or magnetism that all bodies possess for one another, 

 and which the astronomer and ihe optician unconsciously 

 heighten by the very means to which they have recourse, as 

 the particles that float in the air again attach themselves with 

 increased facility by the use of the alcohol. In a similar, but 

 reverse sense, water will not attach itself to many metals, but 

 if they are kept in a horizontal position, the fluid, in its at- 

 tempt to shrink away, will collect itself up into little drops as 

 if the surface were greasy, and it is only prevented from flying 

 away by its density, which condemns it to obey the law of 

 gravitation. This repugnance of water for metals I consider 

 to be the main cause why, dew does not settle upon them, 

 when neighbouring bodies are completely covered by it. 



I had arrived at the preceding convictions, when a dis- 

 covery I made excited in me a degree of surprise that will, I 

 doubt not, be felt by others. Having formed a needle of the 

 fresh specimen of ivory which I have already mentioned, I 

 was tempted some days afterwards, by a movement almost of 

 idle curiosity, as 1 had just succeeded with one of sealing- 

 wax against glass, to test it also with the same substance, when 

 I found that by a mere push of the finger, it attached itself 

 firmly to it. In consequence of this most unexpected result, 

 the ivory needle was tried with all the following substances, 

 and it succeeded in every case at 90° by the mere use of the 

 finger, except with those preceded by an asterisk, for which 

 the magnet was obliged to be employed, and therefore their 

 intensities must be considered a shade lower than those of the 

 others, as well as a few that were lower still, but which have 

 their measurements assi<i;ned. 



The ivory needle would not connect itself with gvpsum, 

 arsenic and aiilimonv, and indeed when the coercing magnet 



