18 PRINCIPLES OF GARDENING. [CH. I. 



eleven to three, in vessels four inches square and 

 half an inch deep, attained the temperatures shewn 

 in this table. 



Wet. Dry. 



Siliceous Sand, bright yellowish gray 99.1 11 '2. 6 



Calcareous Sand, whitish gray . . 99.3 112.1 



Gypsum, bright w^liite gray . . . 97.3 110.5 



Sandy Clay, yellowish 98.2 111.4 



Loamy Clay, yellowish . . . , 99.1 112.1 

 Stiff Clay, or Brick Earth, yellowish 



gray 99.3 112.3 



Fine bluish gray Clay 99.5 113.0 



Lime, white 96.1 109.4 



Magnesia, pure wiiite 95.2 108.6 



Garden Mould, blackish gray . . 99.5 113.5 



Arable Soil, gray ...... 97.7 111.7 



Slaty Marl, brownish red .... 101.8 115.3 



The results of M. Schluber's experiments demon- 

 strate that which our knowledge of the laws of caloric 

 would have induced us to pre-suppose, namely, that 

 light coloured earths by reason of their reiiecting 

 most rays of heat, are warmed much more tardily 

 than dark coloured earths. It was this conclusion 

 which induced me, some years now past, to try the 

 effect of sprinkling coal ashes over rows of autumn 

 sown peas. The peas invariably appeared above 

 "the soil some days before those in rows not similarly 



