an Improved Pluviameter, 
329 
adopted, and which, as far as I have yet tried it, has fully an¬ 
swered my expectations. 
It will be quite clear, that in a perfect calm the rain will fall 
perpendicularly, and consequently the quantity caught in the 
vessels horizontally placed, will be merely as the surface exposed, 
without any correction whatever ; but this, in its strictest sense, 
is rarely, if ever, found to be the case. 
It is equally apparent that if a gale of wind be so exceedingly 
severe (and which we will suppose for the sake of argument) that 
the rain should be blown along the surface of the earth in an 
horizontal direction, no water would be found in the common 
pluviameter. Whatever may be the character of the shower, or 
the quantity of rain fallen, experience shows us that few showers 
are unattended with a certain degree of drift, and that conse¬ 
quently the rain caught in the horizontal pluviameter can rarely, 
if ever, be true. It becomes necessary, in order to get a correct 
estimate, that the surface experimented on should be made to 
change its position, so as to maintain a perpendicular direction 
to the rain : but this method is attended with so many difficulties, 
that I propose to arrive at the same results by a somewhat more 
tedious, though by far more correct, process. 
To obviate these difficulties, I have caused to be constructed 
two pluviameters, of equal area; one like the common rain- 
guage in general use, the other suspended perpendicularly to the 
horizon, with a vane at the top to direct the surface always to 
the wind. 
Those I have in use contain each of them an area of fifty 
inches. One being merely the usual funnel, with an inclined 
margin to prevent the' spattering of the rain into the pluviameter 
from the edge. Of this it will be unnecessary to say more than 
that it is in diameter as nearly as possible eight inches, and is 
placed over a closed cylindrical receptacle, two inches in diame¬ 
ter, which being the sixteenth of the surface will give a suscepti¬ 
bility of measurement sixteen to one of the quantity fallen. 
The perpendicular pluviameter is in form a half cylinder, lon¬ 
gitudinally divided, terminating in a funnel shape at bottom, and 
is surmounted with a vane to direct the aperture to the wind; 
