570 MR EDMUND J. MILLS’S 
thermometer submitted to experiment; it is held suspended yertically by 
a wire, and prevented from touching the sides of the tube by a collar of 
cork at 6 and an open lead helix at c. The upper part of the glass tube 
consists of a T-piece, whose lateral portion serves to carry off steam. By 
taking glass tubes of different lengths it is thus easy to obtain data for calcu- 
lating the unknown coefficient z One precaution, however, is necessary 
to be carefully borne in mind, The level of the liquid in the flask must 
not be allowed to vary much, or to descend below the mark a; otherwise 
heated air from the gas flame below is sure to lap round and overheat 
the emerging steam, thereby rendering all the readings useless. In order 
to entirely remove any source of error from overlap, a screen of tinned sheet- 
iron 61 centimetres square was perforated and dropped over the flask nearly as 
far as a; the subordinate thermometer was also screened. In spite of every pre- 
caution, there appears to be in the experiments some source of variation which 
I could not detect ; and as the value of @ is very small, it became necessary to 
take very numerous readings before constant means could be obtained for it. 
Table I. contains the numerical results furnished by thermometer 2. The 
TABLE I. 
N. 2. N. 2. N. 2. 
393°95 to 310 =| (000153773 |, 392-90 to 210 00014414 | 391°85 to 110 00014435 
393°50 ,, 310 00011323 || 392:22 ,, 210 00014377 | 391:00 ,, 110 00014966 
39104 ,, 290 ‘00013067 | 390:00 ,, 190 ‘00013679 | 388:90 ,, 90 00014065 | 
390:00 ,, 290 00013618 | 588:95 ,, 190 00013605 | 39791 ,, 90 | 00014021 | 
392°11 ,, 290 00014551 | 390°97 ,, 190 00014659 | 589°86 ,, 90 00014777 
395°02 ,; 290 00014724 | 393-76 ,, 185 00015171 | 392°50 , 90 00015749 
39425 ,, 295 00015180 | 393:10 ,, 210 00016206 | 391°90 ,, 105 00015655 
BOS 20. OUT 00015901 | 392°02 ,, 210 00014487 | 390°90 ,, 100 00014095 | 
391:30 ,, 250 00015257 | 390:27 ,, 155 00014905 || 389:27 ,, 85 ‘00016062 
391°90 ,, 280 00013677 | 39057 ,, 180 00015584 | 389-27 ,, 80 00016598 
39245 ,, 280 00015670 | 391:28 ,, 180 (00015720 | 390:19 ,, 80 00015720 
| 39500 ,, 280 00013999 | 397°75 ,, 180 ‘00014817 | 392-70 ,, 85 00015055 
39519 ,, 280 00016433 | 394:00 ,, 180 00015861 | 392:90 ,, 80 ‘00015686 
395°40 ,, 280 00015737 | 394-10 ,, 180 00016832 | 393-00 ,, 80 00016013 
395°75 ,, 290 00014182 | 39429 ,, 190 00016504 | 393-07 ,, 90 00016598 
39500 ,, 290 00013284 | 393°85 ,, 190 00013909 | 392°75 ,, 90 00614327 
| 
Means— : 
393-44 to 288:25 | :00014498 | 392°25 ,, 189°37 | 00015014 | 391°75 ,, 90:94! 00015239 
| 
unit length of N is a millimetre (valued at about 0°25 C.). The lengths given 
as read are each the mean of fifteen readings, and the table involves altogether 
2160 readings. 
