38 WRITINGS OK JOSEPH HENRY. [1855- 



the generalization which this theory so admirably expresses ; 

 and we may safely attribute the apparent want of agreement 

 to our ignorance of some essential condition of the phenom- 

 ena in question, or to some error in the logical deduction 

 from our principles. The history of science abounds in ap- 

 parent exceptions to general rules which when better un- 

 derstood become additional evidences in support of the gen- 

 eral principle. The foregoing remarks will not be thought 

 inapplicable on the present occasion by those who have 

 studied the history of the progress of meteorology. 



One of the most important general truths at which science 

 has arrived by a wide and cautious induction, and which is 

 the foundation of meteorology, is that nearly all the changes 

 which now take place at the surface of the earth are due to 

 the action of the sun. The forces which pertain to the earth 

 itself — such as gravity, chemical affinity, cohesion, electricity, 

 magnetism, &c. — are forces of quiescence; they tend to bring 

 matter to a state of rest at the surface of the globe, from 

 which it is only again disturbed by the solar emanation. 

 All the elementary substances which constitute the surface 

 of our planet, with the exception of the organic matter, have 

 long since gone into a state of permanent combination. The 

 rocks and various strata are principally composed of burnt 

 metals. The whole globe is an immense slag, analogous to 

 that drawn from the smelting furnace, surrounded by a 

 liquid and an aerial envelope ; the former in a state of ulti- 

 mate chemical combination, and the active principle of the 

 latter — the oxygen — finding nothing to combine with, except 

 what has been released from a former combination by the 

 action of the sun. If therefore the solar impulses were sus- 

 pended, all motion on the surface of the planet would cease: 

 the wind would gradually die away ; the currents of the 

 ocean would slacken their pace, and finally come to rest ; 

 and stillness, silence, and death would hold universal reign. 

 We cannot however at present pursue this thought, but 

 must confine our remarks to the effects of those impulses of 

 the sun denominated heat in their connection with meteo- 

 rology. 



