PHYSICS OF THE GLOBE. 157 



fourth, that the excess of rain falling on the latter portion 

 of the tower will, to a large extent, compensate for the de- 

 ficiency on the former portion. 



An appendix to the "Washington Observations for 1874 " 

 contains an investigation by Professor Eastman into the 

 comparative results obtained by using rain-gauges of dif- 

 ferent sizes and patterns. Fourteen gauges were set up 

 in two groups, and established respectively on the south- 

 west corner of the roof, and at the surface of the ground on 

 the lawn. The seven gauges in each set were of similar sizes, 

 and he found but little difference in the quantities of rain 

 caught by gauges two inches or more in diameter. On the 

 other hand, the average quantity received by the set that 

 was established on the southwest corner of the roof was but 

 90 per cent, of that caught by the set on the lawn, 34 feet 

 below. The readings for the roof during steady drizzling 

 rains were 80 per cent, of those for the lawn ; but during sud- 

 den show r ers, generally accompanied by high wind, the per- 

 centage was 92. He concludes that wind has little, if any, 

 influence. 



CHEMICAL AND PHYSICAL PROPERTIES OF THE AIR. 

 Thiesen publishes an interesting memoir on the extent of 

 our atmosphere. Having regard to all that at present is 

 known of the physical properties of air, he finds that contra- 

 dictions arise at almost every step, and that we are not as yet 

 able to indicate the limit of our atmosphere. He has sought 

 to determine how far the circumstances that are ordinarily 

 neglected such as the individual gravitation and the move- 

 ments of the o-ases can affect our views as to the extent and 



CD 



density of the atmosphere surrounding each planet. 



Ebermayer has, in connection with his work at the Bava- 

 rian Forest stations, investigated the quantity of carbonic 

 acid in the air and in the ground, in the forests and in the 

 open field. 



The presence of hydrogen peroxide in rain-water has been 

 investigated by Kern, in a village about ten miles from St. 

 Petersburg. He finds that it is always present during June, 

 July, August, and September, and that it is least in quantity 

 when the rain falls with a northerly wind. 



Schone, of Moscow, communicates to the Berichte of the 



