100 Report on the Instruments employed in, and on the 



The Register Thermometers are of Rutherford's con- 

 struction, and made by Mr. Newman. Those by which the 

 maximum and minimum of the temperature of the air in the 

 shade are ascertained, are placed in an open spot in the 

 Arboretum, skreened from the rays of the sun, and sheltered 

 from terrestrial radiation by a kind of umbrella of oiled cloth ; 

 they are attached to the northern side of the post which 

 supports the umbrella, and stand four feet from the ground. 

 That by which the maximum of heat is ascertained, is filled 

 with mercury ; the one applied to registering the minimum 

 of heat, is a spirit thermometer. 



In addition to these, two other register thermometers of 

 the same construction are used. The first is of mercury, and 

 the ball is covered with black wool. It is placed within 

 four feet of a garden wall, fronting the south, about two 

 inches from a bed of garden mould. It registers the greatest 

 degree of heat under the influence of the sun. The second 

 is of spirit ; its ball is also covered with black wool, and is 

 fixed in the focus of a parabolic metallic speculum, and ex- 

 posed to the full aspect of the sky. It registers the maximum 

 degree of cold arising from radiation in such a situation. 

 It is placed in the Arboretum, near the first described ther- 

 mometer. 



The Rain-gauge is made according to Mr. Howard's 

 directions, in his work upon the climate of London ; it stands 

 upon the level of the ground in the Experimental Garden. 

 The quantity of rain is registered daily. 



The direction of the wind is noted by a vane of the usual 

 construction. 



