1864.J ^27 [Chase. 



A letter of acknowledt>;ment was received from the Chicao;o 

 Historical Society, dated October 8th, 1864. 



Donations for the Library were received from the Bureau 

 of Public Instruction and Public Works, at Paris ; the New 

 England Loyal Publication Society ; Messrs. Blanchard & 

 Lea, and Bishop Stevens. 



The death of Dr. William Pepper, a member of the Society, 

 was announced by Dr. Coates. Dr. Pepper died on the 15th 

 inst., aged 54. Dr. Coates was appointed to prepare an 

 obituary notice of the deceased. 



Mr. Chase made a communication on Terrestrial Magnetism 

 as a Mechanical agent. 



In a note to a former communication, I expressed mj belief that 

 the British Astronomer Royal would find in the mechanical action 

 of the sun's rays, the precise "occasional currents" for which he was 

 seeking, as the probable cause of magnetic storms. Mr. Airy has 

 recently sent me a copy of his very interesting paper, (Trans. Roy. 

 Soc , 1863, Art. XXIX.), and its perusal has greatly strengthened 

 this belief 



All of my meteorological views rest upon the hypothesis, that the 

 atmospheric changes, whether of humidity, temperature, pressure, 

 electricity, or magnetism, are purely mechanical ; and that being con- 

 trolled by the laws of motion, their proper explanation does not re- 

 quire the assumption of any peculiar magnetic or electric fluid, but 

 that a single homogeneous, elastic, and all-pervading aether, may be 

 both the source and the receptacle of all the various forms of force. 

 In its principal features, this theory harmonizes with the now gene- 

 rally accepted belief in the mechanical origin of light and heat, but 

 in its details it involves some new and interesting special applica- 

 tions, which I have endeavored partially to develop. 



It will be readily seen, by a reference to my communication of 

 April 15, (ante, p. 367, sqq.), that the mechanical action of the 

 currents to whose electric action Ampere ascribed the origin of ter- 

 restrial magnetism, produces two opposite spirals in the air and 

 aether, — the lower moving from the poles to the equator, and against 

 the earth's rotation ; the upper from the equator to the poles, and in 

 the same direction as the earth's rotation ; the two being connected 



