BAETH TEMPERATDKE. 127 



we are informed by travellers that tlie temperature in the sun, 

 at Gondar, has been seen to be 113° (Bruce); at Benares 110°, 

 113° 118° (Harvey) ; or at Sierra Leone, 138° (Winterbottom) ; 

 it must be supposed that, in reality, the temperature would 

 have been found much higher in those places had more efdcient 

 means of observation been employed. Mr. Foggo, indeed, 

 succeeded, by means of a large thermometer, having the baU 

 covered with black wool, and fully exposed to the direct rays of 

 the sun, unsheltered from the wind, in obtaining, at Edinburgh, 

 on the 29th of July, at B^ 10" p.m., an indication of 150°, and at 

 3*^ p.m. of 140°, while another instrument, similaxly prepared, 

 and resting in contact with herbage, was found to indicate only 

 119° and 110°; so that, as Mr. Foggo remarks, a difference of 

 30° was produced in these cases solely from the manner in 

 which the instruments were exposed. {EdAnhwrgh Philosophical 

 Journal, No. xxvii.) 



For horticultural purposes a far more extensive series of 

 observations than we at present possess requires to be made at 

 a great number of different places, with a view to determine the 

 connexion between the temperature of the soil and the seasons 

 of vegetation. In making these, the nature of the soil in which 

 the thermometers are plunged should, among other circum- 

 stances, be very precisely described ; for it is obvious that the 

 result will be essentially affected by the peculiar conducting 

 power of the earth. In the meanwhile the two following 

 diagrams, and the observations which follow, for which we are 

 indebted to Mr. Thompson, throw much light upon this obscure 

 subject. 



" It will be seen from the diagram of the mean monthly tem- 

 perature of the earth and air at Chiswick, that the earth, at two 

 feet deep, is warmer than the air by two or three degrees at 

 the commencement of the year ; but the lines representing the 

 progress of the respective temperatures gradually approximate, 

 the ground one falKng and the air rising a little towards the 

 end of February. In March, both take a decided start, and 

 towards the end of that month the lines coincide, and then the 

 air temperature is higher than that of the earth till August, 

 when the contrary takes place. The mean temperature of the 



