37 



Pike's Peak, July $th, 1877. Baromete* 2233, on the outside of the house of the 

 Signal Service. T^vo feet six inches below the highest point of the mountain. 



This table also gives the form in which our observations were taken and kept. 



These facts lead us to infer that, though the aneroid may 

 answer very well for the comparatively small heights of our 

 Eastern coasts, it will hardly do for such great elevations, or 

 for such long distances as are found in the West. It needs 

 constant watching and correcting by comparisons with a 

 mercurial barometer, as its zero point is apt to change by the 

 handling of the instrument. The influence of the tempera- 

 ture, even in those which bear on their face " compensated" is 

 by no means eliminated, and a correction has to be found ex- 

 perimentally for each instrument. It also needs (an idea 

 which few persons having an aneroid seem to realize) con- 

 siderable care in transportation, and an accident to it is whol- 

 ly beyond the possibility of repair in the field, while a mercu- 

 rial barometer, with the aid of a little ingenuity, can be read- 

 ily repaired, if pains have been taken to carry the requisite 

 duplicate parts along with the instrument. 



