310 "European Intelligence. [July, 



VI. That experiments on the decrease of temperature at increasing heights 

 in the atmosphere be recommended as an important subject for the contribu- 

 tions of observers. 



Note. — Series of observations for considerable periods of time on the mean tem- 

 perature of the air at fixed hours, and at stations of which the difference of height 

 lias been accurately measured, are the most valuable. The best hours for observa- 

 tions are those which give most accurately the mean temperature of the period of 

 observation. The hourly observations at Leith Fort have determined the hours 

 which give the annual mean temperature in this country to be about 9f A. M. and 8§ 

 p. m. Experimental balloons have lately been employed by the Earl of Minto, 

 to assist the solution of this problem, which is one of the most interesting in 

 Meteorology : but the investigation of it is nearly brought to a stand for want 

 of sufficiently numerous observations. The observer may be referred for infor- 

 mation to Ramond's Memories sur la For mule Barometriquede la Mecanique Celeste; 

 to the researches of Humboldt ; to Professor Leslie, Supplement to the Encyclopae- 

 dia Britannica, Article Climate; to Pouillet, Elemens de Physique ; to Mr. Atkin- 

 son's paper on Refractions, in the Memoirs of the Astronomical Society : and to 

 Mr. Ivory's Memoir on the same subject in the Philosophical Transactions, and 

 his papers in the Annals of Philosophy. 



VII. That the observation of the temperature of springs at different heights 

 and depths should be pointed out as an object of great interest, in prosecuting 

 which insulated inquirers may render essential aid to science. 



2^ote. — When springs are copious, a few observations in the course of the year 

 suffice to give with great accuracy their mean temperature. The height of the 

 springs above the mean level of the sea, and the depth of Artesian wells, should be 

 carefully observed ; and where the corresponding mean temperature of the air can 

 be obtained, it should be stated. In two points of view these observations are 

 important, independently of the inference which they may furnish as to the de- 

 crease of heat in the atmosphere. The great interest attached to the phae- 

 nomenon of the progressive increase of temperature of the globe, as we descend 

 through the strata, renders of value observations on the temperature of springs at 

 considerable heights, of springs in mines, and of those brought to the surface from 

 some depths by the process of boring. This question has been treated with great 

 success by M. Cordier in several memoirs, some of which have beea translated 

 into English. Again, the researches of Humboldt, Buch, Wahlenberg, and more 

 recently Kupffer, in a Memoir on Isogeothermal Lines, read before the Academy 

 of St. Petersburg in 1329, have shown that the temperature of the earth differs 

 in many parts of the globe from that of the air, being generally in defect below 

 lat. 56°, and in excess beyond it. Artesian wells, and the deviation of the mean 

 temperature of the earth from that of the air in different latitudes, have opened 

 new fields for discussion ; and by the zealous co-operation of observers cannot 

 fail to present results, of which at present we can form but an imperfect idea. 



Magnetism— It appears to the Committee highly desirable, that a series of 

 observations upon the intensity of terrestrial magnetism in various parts of 

 England be made by some competent individual, similar to those which have 

 recently been carried on in Scotland, by Mr. Dunlop. 



