Mil. \V. N. SHAW ON HrGHOMKTKIC METHODS. 



79 



The application of this formula involves the assumption of a value of d, the specific 

 gravity of steam. The difficulties connected with this are discussed in Note A 

 (p. 121). The value '622 has been assumed throughout my experiments. For Xw/V 

 inside the bracket the value of e derived from the temperature of the savurator may 

 be substituted without appreciable error. 



To facilitate computation I have tabulated the values of X, i.e., 760(1 -4- aT)/Ae, 

 for each degree Centigrade as below : 



TABLE for Reduction of Aspirator Observations. 



Table of the value of 7GO (1 + aT)/dA for every degree of temperature between 



- 10 C. and + 30 C. 



d = 0-G22. 



A = 1293 grammes per cubic metre. 



a = -003GG. 



The fraction (E t')/B is always small, and B has therefore always been taken equal 

 to 760. The practical error thus introduced is only of the order '00002. 



3. Before describing the apparatus first employed, it will be well to call attention 

 to the temperature measurement. For this purpose I have been able to avail myself 

 of eleven thermometers ; of these, two, by NEGRETTI, are the property of the Meteoro- 

 logical Office, graduated to half degrees FAHRENHEIT ; two of iny own, by HICKS, are 

 graduated to fifths Centigrade ; two, by HICKS, graduated to fifths FAHRENHEIT, one, 

 by HICKS, graduated to fifths Centigrade, one, by CETTI, graduated to fifths Centi- 

 grade, and three, by GEI&SLER, graduated to tenths Centigrade, are the property of 



