B. TERRESTRIAL PHYSICS AND METEOROLOGY. 61 



channel, at the same depth, the temperature decreased from 

 42.8 to 38.8. 



Attention is called by the author to the temperature indi- 

 cations of the Porcupine expedition in July, 1869, where, in 

 the deep depression of the Atlantic Ocean, outside the chan- 

 nel, while the temperature at the surface was 62.6 Fahr., at 

 2435 fathoms it was 36.5, a decrease occurring abrubtly be- 

 low the first 50 fathoms, through the loss of the influence of 

 the sun's rays, and then, again, at TOO fathoms, the difference 

 between 900 fathoms and the sea-bottom amounting only to 

 2.7. 



Southwest of Iceland, to the west of the Rockali Gulf, at a 

 depth of 300 fathoms, where the sea-bottom branches off from 

 the greatest depression of the Atlantic, a uniform tempera- 

 ture of 44.6 was noted, while at the same depth on the east 

 side of the Rockali the temperature was 48.2. 



In the Faroe-Shetland channel, and to the northeast of Ice- 

 land, at a depth of 200 to 300 fathoms, water was met with 

 of 32 Fahr., while in the neighboring portion of the Atlantic 

 Ocean the temperature at the same depth was above 46.4. 



The general variation of the surface temperature amounts 

 to 9 Fahr. or even more, but becomes less as we descend, 

 the decline, however, not being every where in the same ra- 

 tio. Deep-sea strata reach their maxima and minima a little 

 later than the surface layer. 17 C, October 1872, 315. 



DO GREAT FIRES PRODUCE RAINS? 



Professor Lapham, in the Journal of the Franklin Institute, 

 discusses the question whether the great fires in the North- 

 west, during the months of September, October, and Novem- 

 ber of 1871, especially that which destroyed the greater part 

 of Chicago, had any decided effect upon the weather, either 

 by creating or moving currents of air, or by causing the fall 

 of rain. After a careful consideration of the facts connected 

 with these fires, and the accompanying meteorological con- 

 ditions, as shown by reliable records, he sees no reason to 

 conclude that any of the rains that fell about the same time 

 were due to the cause in question. 



Referring, however, to Mr. Espy's hypothesis of the produc- 

 tion of rain by artificial fires, he calls attention to the fact 

 that Espy only claimed that fires would produce rain under 



