72 



was nearly at right angles with our meridian. And the truth of 

 the result would therefore chiefly depend on observations to deter- 

 mine the latitude of two places nearly north and south of each 



For this commuuication 1 received a special and flattering ac- 

 knowledgement from the Society, and was told that an engraving 

 of the delineation of the eclipse which I had sent would have been 

 made, had not one already been prepared " from a drawing of Mr, 

 Ferrers, who observed the eclipse at Kinderhook, which very 

 closely resembled mine." I have introduced this letter on the 

 present occasion for the purpose of pursuing, to a greater length, 

 some of the ideas suggested in it, and which may lead to a wide 



I have said in my letter to Dr. Rush, that I could not account 

 for the brightness that surrounded the moon, beyond what might 

 be supposed to be her atmosphere, in any other way than by con- 

 sidering that body as possessing phosphoric properties in an emi- 

 nent degree : I shall now make some observations for the purpose 

 of elucidating that remark. 



Light in itself is invisible ; its existence, like that of soul or 

 spirit, can only be known by its efiects or operations perceptible 

 to our senses. The existence of light is made known to us only, 

 either by its rendering visible the body from which it emanates, or 

 the bodies on which it falls. The luminous streams which pro- 

 ceeded from the moon, during the total eclipse of the sun, to the 

 distance of some thousands of miles, could not then be simple 

 light, but some grosser material which either contamed the mat- 

 ter of light in itself, and which was made visible by sending that 

 light to the eye, or it must have been something on which light 

 fell, and was thereby made visible, in the same manner that the 

 common objects that surround us are made visible. 



The latter supposition is inadmissible, because there is no evi- 

 dence that the moon has an atmosphere of any great extent, and 

 therefore there is nothing about her, beyond this, capable to sup- 

 port matter from which light can be reflected, certainly not to the 

 extent of the luminous rays that proceeded from her during the 

 eclipse. The only possible way then, according to 



