156 Wisconsin Academy of Sciences^ Arts, and Letters. 



§ 11, and Book 111, Chap. 1, § 4.) He makes use of it 

 afterwards in discussing the Moon's influence in deter- 

 mining a tide at any point on the surface of the Earth 

 (Book IV, Chap. I, § 1 et seq.) ; her influence on the pro- 

 tuberant mass about the Earth's equator, causing lunar 

 precession (Book Y, Chap. I, § 3 et seq.), and the recipro- 

 cal action of this mass in causing irregularities in the 

 orbital motion of the moon. (Book VII, Chap. II, § 20 

 et seq.) 



The introduction of this function enabled him to do 

 away with difficult — in some cases impossible — integra- 

 tions, and to substitute therefor the comparatively easy 

 processes of difierentiation. 



It seems to have been used by Laplace merely as an 

 Analytical artifice whereby to accomplish certain results 

 in the calculation of attractions, by substituting indirect ^ 

 but, as it proves, easy methods for direct but very difiicult 

 ones. He applies it, of course, only to the force of grav- 

 itation. 



Afterwards, in 1828, the term Potential Function was 

 applied to it by George Green, a poor operative, in Not- 

 tingham, England, whose mathematical labors in the in- 

 tervals of his other labor raised him to such notice as to 

 cause him to be sent to Cambridge at the age of forty ; 

 and to be now regarded as one of the greatest contributors 

 to Mathematical Physics. His paj)ers have recently been 

 published by Messrs. Macmillan & Co. in one volume, 

 edited by Prof. JST. M. Ferrers. They are models of ana- 

 lytical elegance and skill. 



Green's treatment of the Potential is, however, purely 

 analytical. He seems, also, to take it for granted that all 

 that Laplace had already written upon the subject in the 

 case of gravitation was well known to those who heard or 

 read him. He first applies this function to distributions 

 ot Electricity and Magnetism over bodies of various form. 



