48 
the funnel, having no opening into the latter: it serves the necessary 
purpose of preventing the entrance of water from the outside ; and by 
resting on the shoulder of the bottle, it gives steadiness to the funnel. 
4 As to the bottle, a common wine-quart will contain from two to two 
and a half inches of rain on this funnel: but it is better to use a three- 
pint bottle (technically termed a Winchester-quart), which has the 
proportions given in the figure. For an unusual fall of rain may happen, 
when a previous quantity has not been measured out; and it is on such 
occasions that we would wish, more especially, to be certain of the 
amount. 
1 A cylindrical glass of the depth of eight inches, exclusive of its foot, 
and lJj- inch in diameter, serves to make the measure. It is graduated 
into parts, each of which is equal in capacity to the depth of ^ of an 
inch on the area of the mouth of the fonnel. A glass of the above 
size will measure out fifty such parts, or half an inch at once. The 
graduation is conducted on the principle (which is a medium between 
calculation and experiment) that a cylinder of water at a mean tem¬ 
perature, an inch deep 5i and five inches in diameter, weighs 10 ounces 
troy. The hundredth part of this, or 48 grains, is accordingly taken 
for the graduating quantity, and the scale is formed by successive 
additions, at each of which the surface is marked. Considering the 
nature of this operation, which scarcely admits of our going to 
fractions of a grain, I suppose the above standard to be sufficiently 
correct. I have been accustomed to etch the scale on the glass with 
fluoric acid, but it is more conspicuous when engraved at the glass- 
cutter’s wheel. Previously to sending it for this purpose, the whole 
scale should be traced, either on a strip of paper pasted on before it, is 
divided, or in oil paint on the glass itself. A diamond, or steel point, 
may be used for engraving the scale, in default of other means.’ 
This gauge was not in use lately, but when changed I cannot find 
any record. 
The first step in this investigation was to form Tables precisely 
similar to those for the temperature of the air, showing at a glance 
the daily falls of rain on the same day of the year, throughout the series 
of forty-four years, and in this way Tables I. to XII. were formed. 
