B. TERRESTRIAL PHYSICS AND METEOROLOGY. 65 



surveyed a large portion of the so-called " volcanic region " 

 of the Atlantic Ocean, finding the water very deep in that 

 vicinity. Specimens brought up from the bottom appeared 

 to be of undoubted volcanic origin. The Casella-Miller deep- 

 sea thermometer was used on one occasion at a depth of 2040 

 fathoms, two miles north of the equator, in longitude 22 16' 

 west, and indicated a temperature of 35 Fahr., at 1000 fa- 

 thoms 38, and at the surface 81, the air being 80. During 

 the voyage from the Canary Islands to Rio, the temperature 

 at uniform depths was found to vary only about two de- 

 e'rees. JVew York Herald. 



EARTHQUAKE WAVES. 



The self-registering tide gauges of the Coast Survey are 

 doing good work not only in recording tides, but also in 

 catching the fleeting waves produced by earthquakes. One 

 of the first cases of this kind occurred on the Pacific coast in 

 1854. The great earthquake of Africa, in 1870, produced a 

 wave that traveled in one half of a day to Honolulu ; and in 

 one, two, and three days respectively to San Francisco, Mel- 

 bourne, and Yokohama. It is now proposed to use this 

 simple instrument at a number of points in the Mediterranean 

 Sea as a regular means of recording the frequent earthquakes 

 that occur there, where the systematic daily tides are so 

 slight as to be nearly imperceptible. The annual report of 

 the observatory at Sydney, New South Wales, states that 

 the tide gauge at that port has recorded fewer earthquake 

 waves than that at New Castle (a hundred miles distant), 

 probably owing to the more open harbor of the latter. 

 3fonthly Notices B. Astronom, Soc,., February., 1873. 



EATE OF INCREASE OF HEAT IX PENETRATING THE EARTH. 



A new determination of the rate of increase of heat as we 

 descend into the earth has been lately made by Dunker, and 

 the care with which the experiments were conducted gives 

 much value to his results. The observations were made in 

 an artesian well in Sperenberg, Germany, having a depth of 

 about 3900 feet. The well being supplied with water from 

 several springs, it was necessary to avoid the disturbing in- 

 fluence upon the temperature of the circulating water ; and, 

 in order best to secure this end, a small hole was bored at the 



