290 COMPARISON OF THE LIGHT OF THE SUN.AND MOON. 
Wollaston furnishes the following account of his mode of procedure.* 
«The Sun’s light was compared with that of a candle, by admitting a beam of it 
into a room through a small circular hole in a plate of metal, fastened in a window- 
shutter; and a small cylinder of any opaque material being placed in the beam, so as 
to cast a shadow upon a screen, the distance of a candle from the same cylinder (or an 
equal one placed at the same distance from the screen) was varied, until the shadow in 
the line of the candle became equally intense with the shadow in the line of the Sun. 
The direct light of the Moon was compared with the light of a candle in the same 
MANNER evt : 
“Tt appears from the mean of the observations given in No. V. of the Appendix, 
that the light of the Sun is equal to that of 5,563 candles placed at the distance of 
one foot; a result which accords very nearly with that of Bouguer. For he states the 
light of the Sun to be equal to that of 11,664 wax-candles at the distance of 16 inches 
French, which is equivalent to 5,774 wax-candles at the distance of one foot English. 
It appears also from my experiments, that the light of the full Moon is equal to 414 
part of the light of a candle, placed at the distance of a foot; and hence that the Sun's 
light is equal to 5,563 X 144 X Moon's light = 801,072 X Moon's light. Bouguer, 
who differs greatly from me in the comparison of the Moon with a candle, states the 
light of the Sun to be — 300,000 X Moon’s light.” 
The observations referred to, are here transcribed: T— 
* V. Observations of the Light of the Sun, compared with that of a Candle, by Means of Shadows. 
H | D. | z | Numerical Value of the Expres- 
Date of the : 1 > | Distance of the Candle from the sion 
i er aa a e E D E 
; : e through Hole. | lox H naue Qux T 
1799. 
End of May 0.0067 93 >. 19.5 6152 
and .0072 93 | 19.0 5611 
Beginning .0087 93 18.0 4382 
of June. .0093 93 17.5 3965 
0093 à 111.5 20.5  . 98228 
.0098 102 | 14.25 6477 
0098 108 15i ..., 0410 
.0098 .120 | 17.0 6299 
May 28 .0098 d 120 17.5 5944 
| June 19 .0105 e Ai EE 7770 
| 0111 O Hg e 4054 
gaus - D c 190 xe 4463 
| por | 66755 
oe es EE 
5 2 
_ * Philosophical Transactions, 1829, p. St sole, E ie loy oce e ul 
