-1859] WRITINGS OF JOSEPH HENRY. 309 



METEOEOLOGY IN ITS CONNECTION WITH AGRICULTURE. 



PART V. — ATMOSPHERIC ELECTRICITY. 

 (Agricultural Report of Commissioner of Patents, for 1859, pp. 461-524.) 



In this paper we intend to give a sketch of the general 

 principles of atmospheric electricity; — a branch of meteor- 

 ology which has attracted in all ages more attention, and has 

 been regarded with more interest, than perhaps any other. 



The vast accumulation of electricity in the thunder cloud, 

 and the energy exhibited in its mechanical, chemical, and 

 physical effects, have impressed the popular mind with the 

 idea of the great efficiency of this agent in producing at- 

 mospheric changes, and have led to views of its character 

 not warranted by cautious induction. It is frequently con- 

 sidered sufficient in the explanation of an unusual phenom- 

 enon to refer it simply to electricity. References of this kind 

 however are by no means satisfactory, since the scientific 

 explanation of a phenomenon consists in the logical refer- 

 ence of it to a general law ; or in clearly exhibiting the steps 

 by which it can be deduced from an established principle. 

 Electricity is subject to laws as definite and invariable as 

 those which govern the mechanical motions of the planetary 

 system. In one respect indeed, there is a great similarity 

 between them, and it will be seen in the discussion of elec- 

 trical phenomena, that these are referable to forces similar 

 in action to that of gravitation ; and that the mathematical 

 propositions which were demonstrated b}'^ Newton in regard 

 to the latter, have been applied with admirable precision to 

 represent those of the former. 



In giving a general exposition of a subject of this kind, 

 two plans may be adopted : either a series of facts ma}' be 

 stated, and from these a theory gradually developed by a 

 careful induction, or we may begin with the general princi- 

 ples or laws which have been discovered, and from these de- 

 duce the facts in a series of logical consequences. The first 

 method is called induction, the second, deduction ; and they 



