98 On Barometrical Measurements* 



a very distinct idea of the height of a mountain, when we 

 stale it as 1Q000 feet, whereas three miles and some fathoms 

 will impress, the real height much more strongly on the mind. 

 The examples subjoined show the method ; and I presume 

 will require no further illustration to those who are ac- 

 quainted with logarithms. I shall only observe, that in re- 

 ducing the metre to fathoms, I have made use of the report 

 which I found in the Memoirs of the Royal Institution, 

 vol.i., namely, l ni 39*371 English inches : and with respect to 

 the thermometer, I have made use of the well known re- 

 port 100 : 1 SO, those two numbers marking the space of the 

 scale comprehended between the freezing and boiling points : 

 thus in calculation the degrees of Fahrenheit should be di- 



o 



minished 32° for the degrees above the freezing point, and 

 on the contrary with respect to the degrees below melting 

 ice, they must be retrenched from 32°. 



I am your very obedient servant, 



De J — =-. 



January 1809. 



Note — In the first of the following examples I have ap- 

 plied to the least height of the barometer, the difference of 

 the thermometers which are attached to them, because the 

 thermometer was lower than in the other. 



In the second example it is the contrary, because the 

 thermometer attached was highest at the station where the 

 barometer was lowest. The rule is to augment the height 

 of the column of mercury, in the coldest station, by so 

 much as ^-^ as there are degrees of different between 

 the thermometers of correction. The perusal of JS^^lamond's 

 Memoir will greatly assist the reader on this subject. 



Example. 



