322 



Mr. B. Loewy on the Behaviour 



[Mar. 4, 



X 



by 

 AT 



X 



5. In order to decide the question of the "vacuum-correction 

 avoiding the above indicated sources of error, I had three a 

 pairs of thermometers made, each pair of equal shape 

 and size as regards bulb and tube, but these pairs differing 

 in this respect among themselves. These six thermometers 

 were, in the manner which is shown in the annexed figure 

 for one pair of them, enclosed in glass cases, which ter- 

 minated in narrow tubes of about 5 inches in length. One 

 case with its thermometer was left open at the top (A), 

 while the other (A') with the corresponding thermometer 

 was closed by a rapid puff of the blowpipe, without the 

 possibility of heating the enclosed air and thus diminishing 

 the pressure upon the enclosed thermometer. 



There were thus subjected to experiment six thermo- 

 meters, of three different forms, as may be seen from the 

 following description of them : — 



(1) A* (No. 6700), Spherical bulb, diameter of bulb j 

 inch, length of stem 13 inches, enclosed in open 

 case. 



(2) A' (No. 6701), Spherical bulb, diameter of bulb § 

 inch, length of stem 13 inches, enclosed in shut 

 case. 



(3) B (No. 6703), Cylindrical bulb, l T \ inch long, 

 Y 3 ^ inch wide, length of stem 1 5 inches, enclosed in 

 open case. 



(4) B' (No. 6702), Cylindrical bulb, ,1 T V inch long, 

 -jSfj inch wide, length of stem 15 inches, enclosed in 

 shut case. 



(5) C (No. 6704), Spherical bulb, diameter of bulb -J inch, length of 

 stem 27 inches, enclosed in open case. 



(6) C (No. 6982), Spherical bulb, diameter of bulb f inch, length of 

 stem 27 inches, enclosed in shut case. 



The thermometers A, A', B, B' represent the usual form and size of 

 these instruments, while those marked C, C are unusually large, and would 

 hardly be employed except for special purposes. The former had each 

 degree divided into five parts, hence reading by estimation to of a 

 degree, while the latter had each degree divided into ten parts, each of 

 which occupied about the space of one degree in the common form ; y-J^ of 

 a degree of Fahrenheit's scale could thus be read with the utmost accuracy. 



6. The thermometers and the receiver employed in these observations 

 were made by Mr. L. Casella, who took the greatest interest in the purpose 

 of the experiments, and consequently took especial care to make the 

 instruments as perfect as possible. 



* These letters are the same as those used in the succeeding Table of Experiments to 

 designate the different thermometers. 



