Proportion of Rain falling yearly, and its proportion in feveral places. 
At Townly in Lancafhire, obferved by Mr. Townly - - - - 42 4 Inches 
Upminfter in Effex, by Mr. Derham -------- ipi. 
Zurich in Switzerland, by Dr. Sceutcher ------- 32 A 
Pifa in Italy, by Dr. Mich. Angl. Tilli ------- 43 
Paris in France, by M. de la Hire -------- ip 
Lifle in Flanders, by M. de Vaubin -------- 24 
Proportions of the Rain of feveral years to one another. 
At Upminster. 
1700 19 Inches 03 Cent. 
1701 18 69 
1702 20 38 
1703 23 99 
1704 15 81 
1705 16 93 
At Paris. 
2i Inches 38 Cent. 
2 7 7 8 
15 42 
18 51 
21 20 
14 82 
Proportion of the Rain of the feveral feafons to one another. 
1708 
January 
February 
March 
April 
May 
June 
Depth at 
Pifa. 
Depth at 
Upminfter 
Depth at 
Zurich. 
1708 
July 
Auguft 
September 
Odober 
November 
December 
Depth at 
Pifa. 
Depth at 
Upminfter 
Depth at 
Zurich. 
Inch. 
6’ 41 
3 28 
2 65 
1 25 
3 33 
4 9 ° 
Inch. 
2 28 
0 46 
2 03 
0 96 
. 2 02 
2 32 
Inch. 
I 64 
1 65 
1 5 i 
4 69 
1 91 
5 9 r 
Inch. 
0 00 
2 27 
7 21 
5 33 
0 13 
0 00 
Inch. 
1 11 
2 94 
1 46 
0 23 
0 86 
11 97 
Inch. 
3 50 
3 i 5 
3 02 
2 24 
0 62 
2 62 
Half year 
28 82 
16 67 
17 3 i 
Half year 
14 94 
8 57 
35 
The Reverend Dr. Hales, in his excellent Treatife of 
Vegetable Staticks, tells us, that the quantity of 
Rain and dew that falls in a year is, at a medium, 
22 inches, and that the quantity of the earth’s eva- 
poration in a year is at leaf!: 9+4 inches, fmce that 
is the rate at which it evaporates in a hummer’s day, 
from which 9 + 4 Inches is to be deducted 3. 39 
inches, for circulating daily dew, there remains 6. 2 
inches, which 6. 2 inches deduded from the quan- 
tity of Rain which falls in a year, there remains at 
leaft 16 inches depth to replenifh the earth with 
moifture for vegetation, and to fupply fprings and 
rivers. 
Hence we find that 22 inches depth of Rain in a 
year is fufficient for all the purpofes of nature in fuch 
fiat countries as is that about Teddington near Hamp- 
ton-Court j but in the hill countries, as in Lancafhire, 
there falls 42 inches depth of Rain water, from 
which deducing feven inches for evaporation, there 
remains 35 inches depth of water, befides great fup- 
plies from much more plentiful dews than fall in plain 
countries. 
Which vaft ftores feemfo abundantly fufficient to an- 
fwer the great quantity of water which is conveyed 
away by fprings and rivers from thofe hills, that we 
need not have recourfe for fupplies to the great abyfs, 
whofe furface at high water is furmounted fome hun- 
dreds of feet by ordinary hills, and fome thoufands 
of feet by thofe vaft hills, from whence the longeft 
and greateft rivers take their rife. 
R A I N B O W, a meteor in form of a particoloured 
arch or femicircle, exhibited in a rainy Iky oppofite 
the fun, by the rarefadion of his rays in the drops 
of falling rain. 
The Rainbow, Sir Ifaac Newton obferves, never ap- 
pears but where it rains in the funffiine, and may 
be reprefented artificially by contriving water to fall 
in little drops like rain, through which the fun fhining 
exhibits a bow to the fpedator’s eye placed between 
the fun and the drops, efpecially if a dark body, e. g. 
a black cloth be difpofed beyond the drops. 
Anton, de Dominis firft accounted for the Rainbow in 
1 61 1, he explained at large how it was formed by re- 
fradion and reflexion of the fun-beams in fpherical 
drops of water, and confirmed his explication by ex- 
periments made with glafs globes, &c. full of water, 
wherein he was followed by Des Cartes, who mended 
and improved upon his account. 
But as they were both in the dark as to the true ori- 
gin of colours, their explications are defedive, and 
in fome things erroneous, which, it it is one of the 
glories of the Newtonian dodrine of colours, to fup- 
ply and corred. 
The following properties are afcribed to the Rain- 
bow : 
1. That it never appears but in a place oppofite the 
fun ; fo that, when we look diredly at it, the fun is 
always behind us. 
2. That when the Rainbow appears, it always rains 
fome where. 
3. That the conftant order of the colours is, that the 
outmoft is red or Saffron colour ; the next is yellow ; 
the third is green ; the fourth or inmoft is Violet or 
blue ; bur thefe colours are not equally bright. 
4. Two Rainbows appear together, one of which is 
higher and larger than the other, and fhews the afor6- 
faid colours, but in an inverted order. 
5-_ The Rainbow is always exadly round, but does 
not always appear equally entire, the upper or lower 
parts being very often wanting. 
6. Its apparent breadth is always the fame. 
7. That thofe, who ftand upon plain low ground, 
never fee above half its circle, and oftentimes not fo 
much. 
8. The higher the fun is above the horizon, the lefs 
of the circle is feen, and, if there be no cloud to 
hinder, the lower, the more of it. 
9. That never any Rainbow appears, when the fun is 
above 41 degrees 46 minutes high. 
Lunar (Rainbow :) The moon alio fometimes exhibits 
the phenomena of an iris or bow by the refradion of 
her rays in the drops of rain in the night time. 
Ariftotle 
