248 OUTLINES OF NATURAL PHILOSOPHY. 



In this formula, the expansion for the temperature of 

 one degree is .004 ; according to the formula of 

 Sir GEORGE SHUCKBURGH and General ROY, it is 

 .00441 



The former expansion agrees very well with the rate 

 and law of expansion, stated in the last section, 

 from the experiments of DALTON and GAY LUSSAC. 

 The expansion in the English formula is therefore 

 probably too great, though the barometric results 

 deduced by means of it agree very well with obser- 

 vation. 



It were, however, better to introduce the true expan- 

 sion, which may be done by increasing the con- 

 stant multiplier by 49, or, which is nearly the same, 



by . 

 <g 



This formula, giving li in fathoms, using also the true 

 expansion, and the centesimal thermometer, will then 

 become, 



h= 10050(1-| ; + *) J log ^ TTKTvnjT 7^ 



1000 / 3 ft (1 + 00018 (q f) 



The addition to be made on account of 'the 50 added 

 * to the constant multiplier, is very easy, as it only 

 requires the difference of the logarithms, or the ap- 

 proximate height, to be increased by a two hun- 

 dredth, or the half of a hundredth part. In prac- 

 iice, the centesimal thermometer will be found by 



much 



