PHYSICS OF THE GLOBE. 205 



diminution of the temperature of the air. The law of this 

 diminution is, according to him, fixed by the mechanical the- 

 ory of heat, and Lubbock, in 1856, was the first to find the 

 solution to this question by starting with the principles of 

 this theory. The present essay dates from 1867, or earlier. 

 By the aid of the mechanical theory of heat, as developed by 

 Thomson and MendeliefF, but with still further generaliza- 

 tions as deduced by himself, Kowalski finds first, during 

 winter the diminution of temperature with altitude is, on 

 the average, very small, and it augments in proportion as 

 the temperature observed near the surface of the earth be- 

 comes higher; second, during the heat of summer the dimi- 

 nution of the density of the layers of air near the surface of 

 the earth can become very feeble, so that the least force suf- 

 fices to disturb the stability of the equilibrium of the layers, 

 which case can rarely happen during winter; third, the va- 

 riation of temperature in a higher stratum of atmosphere 

 always manifests itself by the relatively greater variations 

 taking place between the lower layers. 



Kowalski's volume is, therefore, of interest to the meteoro- 

 logical observer principally because of its bearing on the 

 question of the temperature of the air. 



The important Experiments on Fog -signals, by Tyndall 

 and others, under the auspices of the Elder Brethren of the 

 Trinity House, have an important bearing upon meteorolog- 

 ical matters, as they apparently give us a new method of ex- 

 ploring the atmosphere ; in fact, as the spectroscope tells us 

 of the total amount of moisture in a great length of the at- 

 mosphere, so do TyndalPs aerial echoes tell us of irregulari- 

 ties in density throughout a circle of many miles in diameter. 

 Practically, however, the most important result of the Trin- 

 ity House experiments has been to definitely establish the 

 fact that two to four ounces of gun-cotton exploded 1000 

 feet above the sea by a rocket give forth such a volume of 

 sound, and the sound-waves are so little affected by echoes 

 or acoustic opacity, as to immensely surpass all other meth- 

 ods of foo--sio-nalin hitherto tried. Such discharges were 

 heard very loud at six miles, distinct, as distant thunder, at 

 fifteen miles, and with a rumbling detonation at twenty-five 

 miles. "A signal of great power, handiness, and economy is 

 thus placed at the service of our mariners." 



