POLYTECHNIC ASSOCIATION. 



963 



of expansion for 1°C .00018153, by the number of degrees C, and the 

 product by the height in millimeters, and subtract the last product 

 from the apparent height. 



The co-efficient of the expansion of glass, for each degree, is 

 .0000092, and of brass, .0000188. Where the scale is of one of these 

 materials, its co-efficient must be subtracted from that of mercury. 



51. Table for correction of Barometric Indications, measured by 

 wooden scale in millimeters, calculated from the co-efficient of Reg- 

 nault, .918153 the dilation of mercury, from Q°C. to 100° C. That 

 for 1° C. is .00018153. 



Multiply the co-efficient for the number of degree C, by the apparent 

 height in millimeters, and subtract the product from the apparent 

 height. 



52. The following table gives the factor e : 



Table of the tension of aqueous vapor, expressed in millimeters of 

 mercury, at 0°C for each degree from 0°C to 35°C {Regnault). 



