McCLURE'S ACHIEVEMENT AND TRAGIC DEATH, 1897 



could be applied to the problem in hand ; especially 

 because it admits of using the isobaric charts with 

 great freedom and effectiveness, thereby increasing the 

 reliability of the result to a marked extent. 



The reduction made, there remained for the final 

 calculation the following data : 



Barometric pressure at the summit of Rainier 17.708 inches 



Barometric pressure at mean base 30.130 inches 



Mean temperature of air column 49 deg. F. 



Latitude of Mount Rainer 46 deg. 48 min. 



In making the calculation I used the amplified form 

 of Laplace's formula given in the recent publications 

 of the Smithsonian Institution, with the constants 

 there adopted. Perhaps for the general reader it 

 may be important to remark that this formula, besides 

 the barometric pressures, contains corrections for the 

 temperature of the air column ; for latitude, and for 

 the variation of gravity with altitude in its effect on 

 the weight of the mercury in the barometer ; for the 

 average humidity of the air ; and for the variation of 

 gravity with altitude in its effect on the weight of the 

 air. I used the latest edition of the Smithsonian 

 tables, but afterward verified the result by a numerical 

 solution of the formula the altitude being, as stated 

 at the beginning, 14,528 feet above sea level. 



It should be noted as an evidence of the great care 

 and foresight with which Professor McClure planned 

 his work and the success with which he carried it out, 

 that the result of his observations agrees within nine 

 feet with that obtained by the United States Geological 

 Survey in 1895, using, as we may suppose, the most 

 refined methods of triangulation the latter estimate 

 being 14,519 feet. In connection with so great an 

 altitude, nine feet is an insignificant quantity, and the 

 close correspondence in the results of the two methods 

 of measurement is truly remarkable. I am not inclined 

 to regard it as accidental, but as due to the most careful 

 work in both cases. 



191 



