-1859] WRITINGS OF JOSEPH HENRY. 37 



plete solution of the problem of the currents of the atmos- 

 phere, even with the greatest possible extension of human 

 science, extremely doubtful. We must therefore be content 

 with approximations deduced from general principles com- 

 bined with the results of extended, precise, and definite ob- 

 servation. 



The history of meteorology illustrates the fact, that what 

 may be termed popular observations and experience, without 

 scientific direction, seldom lead to important rules. The 

 uneducated sailor of to-day, after three thousand years of ex- 

 perience, firmly believes that he can invoke the winds and 

 entice them from the caves of iEolus by a whistle. Most of 

 the aphorisms in reference to the changes of the weather, 

 though of venerable antiquity, merely relate to the greater or 

 less degree of moisture in the atmosphere. They declare 

 what has happened, that a change has already taken place 

 in the air, but give no certain indication of what is to occur. 

 In order therefore to the successful study of meteorology, the 

 results of systematic observations are to be compared with the 

 deductions from well established principles of science, and 

 the converse; or in other words, deduction and observation 

 should constantly go hand in hand, the former directing the 

 latter, and the latter correcting the conclusions of the former. 



In meteorology, as in all other branches of science, the im- 

 portant rule adopted by Newton should never be neglected, 

 namely : " No more causes are to be admitted for the explan- 

 ation of any phenomenon, or class of phenomena, than are 

 true and sufficient." Though a general principle which is 

 in strict accordance Avith the established laws of force and 

 motion cannot be immediately applied to the explanation of 

 an isolated class of phenomena, it is not, on that account, to 

 be set aside for some new and unknown agent. We must 

 look to farther investigations for the light which shall 

 enable us to perceive the connection. The undulatory theory 

 of light connects so many facts, and has enabled the scientist 

 to predict so many others which were previously unknown, 

 that though a few outstanding phenomena may still exist 

 they do not militate against our convictions of the truth of 



