Rowland's Thermometers mth the Paris Standard. 3 



Pennsylvania, and was not available for this comparison. 

 The three Baud in thermometers were numbered 6163, 6165, 

 and 6166. Of these, 6163 was used in eight experiments, 



6165 in one experiment, and 6166 in four experiments. 



6166 was also compared by Joule with one of his own ther- 

 mometers. (Rowland, Proc. Am. Acad. xvi. p. 38, 1880.) 

 The three Tonnelot thermometers were numbered 11800, 

 11801, and 118 LI, and were made between November 1895 

 and January 1896. A complete study of these was made by 

 the International Bureau, including a comparison at several 

 points with the standards of the Bureau which had previously 

 been compared with the hydrogen thermometer. Two of the 

 thermometers, 11800 and 11811, were broken during their 

 first transportation to America, but through the liberality and 

 kindness of the International Bureau and of M. Guillaume, 

 they were repaired by the maker, and a completely new study 

 of them was made. These Tonnelot thermometers were made 

 of French " verre dur/ J with transparent stems, and were 

 divided into tenths of a degree. 



The Baudin thermometers were divided into millimetres. 

 The centimetre marks were numbered, and corresponded in 

 a rough way to degrees. The following table gives the 

 dimensions and other data concerning these six thermo- 

 meters : — 



Table I. 



Constants of Thermometers. 

 Tonnelot Thermometers. 



Numbers 11800 11801 



Division T V degree T V degree 



Total length 701mm. 704 mm. 



Middle of bulb to zero of scale ... 55*8 mm. 59*0 mm. 



Length of a " degree " of the scale. 5'86 mm. 5'858 mm. 



Value in degrees centigrade of 

 one " degree" of the scale .... 0°'870604 1°'000014 



Baudin thermometers. 



Numbers 6163 6165 



Division millimetres. millimetres. 



Total length 501mm. 500 mm. 



Middle of bulb to zero of scale ... 34 mm. 37 mm. 



Value in degrees centigrade of 



one centimetre on stem 1°'114 o, 8470 



B2 



11811 

 T V degree 

 679 mm. 

 74-3 mm. 

 8'91 mm. 



0°'977160 



6166 



millimetres. 



497 mm. 



34 mm. 



0°-779 



