B. TERRESTRIAL PHYSICS AND METEOROLOGY. 41 



B. TERRESTRIAL PHYSICS AND METEOROLOGY. 



RATIO OF BAROMETER DEPRESSION TO THE HEIGHT 



OF THE TIDES. 



At a meeting of the Philosophical Society of Washington, 

 Professor William Ferrel presented an account of some exper- 

 iments in which he had been engaged at the request of the 

 superintendent of the Coast Survey, for determining the in- 

 fluence of the barometric pressure upon the tides. Taking 

 the observations made with the tide-gauge at Boston Harbor, 

 he compared them, hour by hour, for a certain period, with 

 the barometrical records of Harvard Observatory, and ascer- 

 tained that, in general, a fall of the barometer of one inch 

 was accompanied by an increased height of the tide of seven 

 inches. The theoretical ratio should be one inch to about 

 thirteen and a half; but the shallowness of Boston Harbor, 

 and the numerous obstructions to the free flow of the water 

 in and out of it, are assigned as the cause of the difference. 

 Similar observations made at Liverpool showed that the tides 

 varied ten inches in height with one inch of barometric fluc- 

 tuation. Wm. Ferrel, Prof. Washington Phil. Soc. 



CROLL OX CARPENTER'S THEORY OF OCEAN" CURRENTS. 



In a third part of his memoir on ocean currents, lately pub- 

 lished in the London, Edinburg, and Dublin Philosophical 

 Magazine, Mr. James Croll examines critically the theory of 

 a general oceanic circulation, put forth by Dr. Carpenter in a 

 paper read before the Royal Geographical Society. After 

 showing that no additional power is obtained from a vertical 

 descent of the polar waters through the action of cold (the 

 "primum mobile" of Dr. Carpenter) above that which is de- 

 rived from the full slope, of less than eighteen feet, due to 

 difference of temperature between the equatorial and polar 

 regions of the sea, Mr. Croll endeavors to prove that the 

 "primum mobile" has in reality no existence, and that, since 

 the energy derived from the whole slope comprehends all 

 that can possibly be obtained from gravity, there is not, in 

 this, sufficient power to produce the circulation which Dr. 



