OF TEMPERATURE. 95 



the healthy condition of many plants. From some 

 interesting observations communicated to me by Sir 

 John Herschel, it appears that the temperature of the 

 earth, at the Cape of (rood Hope, is often excessive. 

 On the 5th of December, 1837, between one and two 

 o'clock in the day, he observed the heat, under the 

 soil of his bulb garden, to be 159° ; at 8 P. M. it was 

 150°, and even in shaded places 119° : the tempera- 

 ture of the air in the shade, in the same garden, at the 

 same period, was 98° and 92°. At 5 P. M. the soil of 

 the garden having been long shaded, was found to 

 have, at 4 inches in depth, a temperature of 102°. 

 " On the 3d of December, a thermometer buried i inch 

 deep, in contact with a seedling fir of the year's plant- 

 ing, quite healthy, and having its seed-leaves, marked 

 as follows:— at llh. 25 m. A. M. 148-2°, at Oh. 48m. 

 P. M. 149-5°, at lh. 34m. p. M. 149-8°, at lh. 54m. P. 

 M. 150-8°, and at 2h. 46m. p. M. 148°." Sir John 

 Herschel observes that such observations "go to show 

 that at the Cape of Good Hope, in the hot months, 

 the roots of bulbous and other plants which do not 

 seek their nourishment very deep, must frequently, 

 and, indeed, habitually, attain temperatures which 

 we can only imitate in our hothouses. by actually sus- 

 pending over the soil plates of red-hot iron. For it 

 must be remarked, that heating the ground from be- 



Lantao, China 



Water of rice fields 113°;|Meyen. 

 adjacent sandy soil 

 much higher; for to- 

 wards midday the 

 black sides of the boat 

 were 142°50. 



