British Associatioiifor the Advancement of Science. 233 



which the difference of height has been accurately measured, are 

 the most valuable. The best hours for observation are those which 

 give most accurately the mean temperature of the period of obser- 

 vation. The hourly observations at Leith Fort have determined the 

 hours which give the annual mean temperature in this country to 

 be about 9^ A.M. and 8i P.M. Experimental balloons have lately 

 been employed to assist th3 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 obser- 

 vations. The observer may be referred for information to Ramond, 

 Memoires sur la Formule Barometrique de la Mecanique Celeste ; to 

 the researches of Humboldt ; to Professor Leslie, Supplement to 

 the Encyclopcedia Britannica, Article Climate ; to Pouillet, Elemens 

 de Physique; to Mr. Atkinson'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 dif- 

 ferent heights and depths should be pointed out as an object of 

 great interest, in prosecuting which insulated inquirers may render 

 essential aid to science. 



Note. — When springs are copious, a few observations in the course 

 of the year suffice to give with great accuracy their mean tempera- 

 ture. 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 ob- 

 tained, it should be stated. In two points of view these observa- 

 tions are important, independently of the inferences which they may 

 furnish as to the decrease of heat in the atmosphere. The great 

 interest attached to the phsenomenon of the progressive increase of 

 temperature of the globe, as we descend through the strata, ren- 

 ders of value observations on the temperature of springs at con- 

 siderable heights, of springs in mines, and of those brought to the 

 surface from some depths by the process of boring. This question 

 lias been treated with great success by M. Cordier, in several Me- 

 moirs, some of which have been translated into English, .^gain, the 

 researches of Humboldt, Buch, Wahlenberg, and most recently 

 Kupffer in a Memoir on Isogeothermal Lines, read before the Aca- 

 demy of St. Petersburg in 18'i9, 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. 

 The progressive increase of temperature with that of the depth in 

 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 i;lea. 



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 indivi- 



N.S. Vol. 11. No. 63. March 1832. 2 H dual, 



