376 NOTES OF A NATURALIST. 



the results of observation, and for this object the only existing 

 materials are to be found in the records of balloon ascents, and 

 in the observations made on high mountains. In balloon 

 ascents the temperature at any considerable height is free from 

 the disturbances caused by the vicinity of the earth's surface, 

 and the results might be expected to contribute to the more 

 accurate determination of the amount of atmospheric refraction. 

 For the measurement of heights by the barometer, it would 

 appear safer to rely on such information as may be gleaned 

 from mountain observations. 



Of balloon ascents by far the most important are those 

 achieved in 1862 by Messrs. Glaisher and Coxwell, to which I 

 have referred in a preceding page. Mr. Glaisher has given in 

 his report a full record of the actual observations made in the 

 course of his eight ascents, and has explained the processes by 

 which he constructed the successive tables, from which he 

 deduced as the final result a continuous decline (unbroken save 

 in a single instance) in the rate of decrement of temperature 

 found in passing through each successive zone of 1000 feet, in 

 ascending from the sea-level to a height of 29,000 English feet. 



I am not aware that the processes employed by Mr. Glaisher 

 in obtaining these results have ever been subjected to such 

 close scrutiny as their importance demands, and as I have 

 found on careful examination that his results are not borne out 

 by the actual observations, I am forced to express my dissenf 

 from his conclusions. The admiration due to the courage, skill, 

 and perseverance displayed by Mr. Glaisher throughout these 

 memorable ascents will not be lessened if we should find it 

 necessary to modify the inferences which he has drawn from 

 them. 



The full discussion of Mr. Glaisher's observations involves 

 an inconvenient amount of detail, and such readers as may 

 be disposed to enter more fully into the subject I must refer to 

 an article in the London, Edinburgh, and Dublin Philosophical 

 Magazine. 



The general conclusions to which I have arrived from the 

 observations made under a clear or partially clear sky is, that 

 the average results show a rapid fall of temperature in the zone 

 extending to about 5000 feet, or 1500 metres, above the earth's 

 surface, and that, within that limit, the rate of fall diminishes 



