TRANSACTIONS 



OF 



THE CROYDON MICEOSCOPICAL AND 

 NATURAL HISTORY CLUB. 



1893-94. 



110. — Eabth Temperatures. 



By De. H. Franklin Parsons, F.G.S. 



(Bead February 8th, 1893.) 



As a small contribution to the proceedings of the Croydon 

 Microscopical and Natural History Club, which has done me the 

 honour to elect me as its President, I submit some observations 

 which I have made during 1892 on the seasonal variations of the 

 temperature of the earth at depths of 1 ft. and 4ft. below the 

 surface. But as these by themselves would be rather a meagre 

 bill of fare to set before you, I propose to supplement them by a 

 short sketch of what is known as to the temperature of the upper 

 layers of the earth at different seasons and different depths. My 

 observations were made at Park Hill Rise, at an altitude of about 

 250 ft. above the sea, under grass, the soil being stiff clay (a 

 small outlier of the London clay). The thermometers were made 

 specially for me by Mr. Denton of Hatton Garden. The bulb is 

 enclosed in an outer shell to retard the movement of the mercury, 

 so that it may not change during the act of withdrawal and 

 reading. The thermometers are graduated on the stem, each 

 degree measuring jL in. They have not been verified at Kew, 

 but when placed together in a water bath the readings of the two 

 agree to a tenth of a degree Fahr. They are let down by brass 

 chains into pieces of iron gas-pipe driven vertically into the 

 ground to the required depth ; one end of the chain is attached 

 to a loop on the top of the thermometer, the other to a cork, 

 which closes the upper end of the tube, over which a flower 



