|Horace-Benedict de Saussure, pioneer of Mt Blanc,|
with barometer case in background
The accurate determination of these requires the careful use of instruments, and the reduction of observations, both processes involving more trouble than unscientific travellers are willing to bestow.
n government surveys, and is available for altitudes up to about 8000 feet ; but, whether its accuracy beyond this limit has yet been sufficiently tested, may be doubted. A useful little pamphlet, explaining the use of these two instruments, has been published by Elliot Brothers, 30, Strand.