UNCERTAINTY OF MODERN METEOROLOGY. 23 
that the annual fall of rain on the roof of the observatory at 
Paris is two inches less than on the ground by the side of it, 
we mnay see that the height of the rain-gauge above the earth 
is a point of much consequence in making estimates from its 
measurements.* The data from which results have been de- 
duced with respect to the hygrometrical and thermometrical 
conditions, to the climate in short, of different countries, have 
very often been derived from observations at single points in 
cities or districts separated by considerable distances. The 
tendency of errors and accidents to balance each other author- 
izes us, indeed, to entertain greater confidence than we could 
otherwise feel in the conclusions drawn from such tables; but 
it is in the highest degree probable that they would be much 
modified by more numerous series of observations, at different 
stations within narrow limits.t 
material life are performed. They give the rise and fall of the mercury at 
heights arbitrarily taken, without reference to the relations of temperature to 
human interests, or to any other scientific consideration than a somewhat less 
liability to accidental disturbance. 
* Careful observations by the late lamented Dallas Bache appeared to show 
that there is no such difference in the quantity of precipitation falling at 
slightly different levels as has been generally supposed. The apparent differ- 
ence was ascribed by Prof. Bache to the irregular distribution of the drops of 
rain and flakes of snow, exposed, as they are, to local disturbances by the cur- 
rents of air around the corners of buildings or other accidents of the surface. 
This consideration much increases the importance of great care in the selec- 
tion of positions for rain-gauges. 
But Mr. Bache’s conclusions seem not to be accepted by late experimenters 
in England. See Quarterly Journal of Science for January, 1871, p. 123. 
+ The nomenclature of meteorology is vague and sometimes equivocal. 
Not long since, it was suspected that the observers reporting to a scientific 
institution did not agree in their understanding of the mode of expressing the 
direction of the wind prescribed by their instructions. It was found, upon 
inquiry, that very many of them used the names of the compass-points to 
indicate the quarter from which the wind blew, while others employed them 
to signify the quarter towards which the atmospheric currents were moving. 
In some instances, the observers were no longer within the reach of inquiry, 
and of course their tables of the wind were of no value. 
‘‘ Winds,” says Mrs. Somerville, ‘‘are named from the points whence they 
blow, currents exactly the reverse. An easterly wind comes from the east; 
