288 



Lord Kelvin on the Statistical Kinetic 



Dr. Chree's Report on Temperatures of Thermometers 

 under Black Cloth and under White Cloth. 



National Physical Laboratory 



(Kew Observatory Department), 



Richmond, 27th July, 1905. 



Experiments ivith two ordinary Thermometers, 

 Nos. 1184 & 1207. 



Thermometers placed horizontally on small stands fastened 

 to the outside window-sill of the wooden room on the Obser- 

 vatory roof, some 40 feet above the general level of the ground. 

 The arrangement was as shown diagram matically. 



N. 



Thermometer . 



Thermometer. 



The north side of this upper room is entirely in the shade until 

 well on in the afternoon. The cloths were wrapped several 

 times round the bulbs and a small adjacent part of the stems. 

 The thermometers were interchanged and the cloths were 

 interchanged to eliminate difference between position and 

 between thermometers. Headings were taken at intervals 

 throughout two days. In every single case the (corrected) 

 reading was higher for the thermometer with the black cloth. 

 The conditions at the time were noted either as (a) bright 

 sunshine, (b) sun shining through cloud ; (c) cloudy, {d) black 

 cloud, i. e. dark generally. 



An analysis appears in the following sheets. The readings 

 are all centigrade, corrected for scale errors. 



Woollen Cloths. 

 July 12. Position on Eight. Position on Left. Excess of Reading under Black 



Black Cloth. White Cloth. 



Time. No. 1184. No. 1207. No. 1184. No. 1207, 

 o o o o 



239 ... ... 22-7 



25-8 



11.0 

 20 

 40 



12.0 

 20 

 40 

 2.0 

 10 

 20 

 SO 

 40 

 50 



26-2 

 25-5 

 25-6 

 26 : 5 

 26-4 



26-8 

 250 

 26-3 



25 V 8 

 27-4 



o 

 23-4 

 24-6 

 24-1 

 25-3 

 249 

 25-6 



23-8 

 24-5 



24 : 8 

 25 : 8 

 25-2 



Cloth, conditions bein^ 



00 (») (<0 



o 

 1-2 



24 



2-2 



1-0 



24 



10 

 09 



0-8 



0-7 

 0-9 



