214 
HINTS TO TRAVELLERS. 
Atmospheric Circulation, by A. Buchan, m.a., ll.d., contains valuable 
statistical information on thermometric and barometric observations in 
different parts of the world, and a series of charts of the world showing 
isothermal and isobaric lines for every month of the year.) The charts 
published by the Meteorological Office refer to the ocean only, but they 
have the advantage of being quarterly, and are therefore preferable when¬ 
ever the traveller’s station is near the coast. It seems impossible to 
compress the information given by these charts into a form suitable to 
these pages, especially as the mean barometric height sometimes varies 
greatly in neighbouring places. The distance from Takutsk in Siberia 
to the Sea of Okhotsk is only 500 miles, yet in winter the calculated 
mean heights of the barometer at these two places, when reduced to sea- 
level, differ as much as 0*8 inch. From the latitude of Valdivia in 
S. America to Cape Horn, the distance is 900 miles, and the mean 
difference of barometric pressure is 0*5 inch. Vancouver’s Island 
is another district where the mean barometer differs much at moderate 
distances. 
“Whenever the observations at the upper and lower stations are not 
strictly simultaneous, or when the mean barometer is taken in place of 
the lower station, the correction for diurnal variation must not be 
omitted, especially in the tropics, where, in other respects, the barometer 
is very steady. The mean amount of diurnal variation in different parts 
of the world is also given in Berghaus’ maps. An error of one or two 
hundred feet might often be caused by the neglect to allow for it. 
The traveller cannot be too strongly urged to have his boilicg-point 
thermometer verified both before starting and after returning. Their 
index error is apt to vary, the thermometer reading lower than it should 
do after frequent use. This is especially the case for the first few years 
after they are made. 
By Barometer or Aneroid , 
The small but complete tables (pp. 217,218) will be especially useful to 
those who carry a mountain barometer and are anxious to make accurate 
determinations, but are not furnished with larger tables. These are 
calculated by Loomis, and are extracted from Guyot’s collection. 
