1883.] EemarJcs ly Mr. Blanford on Br. WartVs paper, 87 



The latter rows o£ figures show that the change of temperature was a 

 gradual one from 4 feet to 66 feet. 



11. From this we have two conclusions : First, that the change of 

 temperature observed at 66 feet compared with that observed at 4 feet is 

 principally owing to the difference in height and not to the presence of 

 trees. Secondly, we conclude that the change of temperature effected by 

 an elevation to QQ feet will be exceeded when a still greater elevation will 

 be tried. An elevation to 100 feet will no doubt produce a corresponding- 

 ly greater change of the minimum temperature, still smaller daily range, 

 still more regular distribution of vapour tension during each day. It would 

 be interesting to find by experiment at what height these extraordinary 

 changes will cease and make room for the ordinary changes which the 

 diminished pressure only accounts for. 



Mr. Blanfoed remarked that the system of observation described in 

 Dr. Warth's report was the inception of a scheme which had been arrang- 

 ed with the concurrence of Dr. Brandis, for the purpose of ascertaining 

 the effects of forests upon the climate in India. It was intended to esta- 

 blish a system of comparative observations somewhat similar in kind to 

 those which had been carried on for some years by Dr. Ebermeyer in 

 Bavaria, and the results of which were published in his well known work. 

 It consisted in obtaining observations of temperature, humidity, rainfall 

 &c., in the forest and the open, both near the ground and at the elevation 

 of the tree tops. Hitherto at Dehra, only the observatory in the open 

 had been actually established, but it was intended to make similar observa- 

 tions in the forest of the Dun. 



The observations as yet on record show that in the winter months the 

 •differences of temperature near the ground and at no greater height above 

 it than 70 feet are very considerable, the minimum temperature before 

 sunrise being from 58° to 9'6° lower at 4 feet above the ground than at 70 

 feet; and the maximum from 03° to 2'6° higher. The latter difference 

 was less than the former partly owing to convection, viz-, the rise of the 

 heated air and the descent of the cooler air above ; and it might be noticed 

 that despite this intermingling the temperature decrement with elevation 

 at the hottest time of day averaged 1° Fahr. for 43 feet, whereas 1° in 183 

 feet is the limit of vertical static equilibrium. Convection must therefore 

 be very active in most months. 



Observations similar in general character to those of Dr. Warth had 

 been carried on for nearly 4 j^ears at the Alipore Observatory, the differ- 

 ence of elevation being, however, not so great. The thermometer cages 

 were at 4 feet and 40 feet ; both exactly similar in exposure. In their 

 general character, the results of these observations agreed with those of 

 Dr. Warth's ; but the complete annual series showed that it was only in 



