186 Mr. Hinds on Climate in connexion 



directions, and with a general resemblance ; the one occurs 

 with the latitude, the other with the elevation through the 

 atmosphere. Already the decrease of temperatiu'e with the 

 former has been noticed ; it remains to speak of a similar cir- 

 cumstance in the latter. Saussure was one of the earliest in 

 noting observations on this subject, and subsequent expe- 

 rience has confirmed their accuracy. Still the differences 

 among observers are even now considerable ; and it appears 

 to be a circumstance subject to numerous disturbing agents. 

 The seasons of the year aflect it, for in summer Saussure 

 found the thermometer to sink 1° for 292 feet of elevation, 

 whilst in winter it required 419 feet to produce the same. 

 Raymond's observations approach those of Saussure ; he 

 found it required 299 feet. Aubuisson gives 315 feet as 

 equal to 1° of depression. Gay-Lussac conducted his obser- 

 vations on a more extensive scale, and in the summer he 

 ascended from Paris to the surprising height of 22,960 feet; 

 for the whole distance 341 feet were found to be equivalent 

 to 1'^ of the thermometer. As the decrease is now known not 

 to be uniform, and the observations of Gay-Lussac were not 

 made at regular intervals, their value is very trifling. Besides, 

 they were made in open space, and are likely to give a very 

 different result to others made at certain gradations on the 

 slope of a mountain. Some simultaneous observations were 

 made at Geneva and Mount St. Bernard, which give 352 feet. 



Observations have not been wanting in the British Isles. 

 From the results it appears, that it requires here a less eleva- 

 tion to effect the same changes in the temperature than on 

 the continent of Europe. Sir Thomas Brisbane and Mr. Wm. 

 Gilbraith found it to be 212 feet in heights of 2000 or 3000 

 feet. Mr. Hewitt Watson has conducted similar experiments, 

 and has communicated the minutiae of his proceedings with 

 an unreserve that gives them an additional value. Unfortu- 

 nately he himself registered the observations at the heights 

 and bases of the mountains, which sometimes embraced an 

 interval of several hours. He also mentions that observations 

 made on the same spot at different times varied considerably, 

 being a confirmation of the opinion expressed above. Several 

 temperatures were registered among the highland mountains ; 

 they fluctuated much, and the mean of the whole gave 216 

 feet for 1°. Further observations, made in Cumberland du- 

 ring warm and dry weather, gave 298 feet ; and in Caernar- 

 vonshire in cold and moist weather 212 feet. This is the re- 

 verse of what Saussure had observed in different seasons. 



The observations made on the contiuent, taken together. 



