Chemistry and Physics. 421 
Description of shade. Loss of light. 
Clear glass, $i tiiny gt Pe aaae - 10°57 per cent. 
Ground glass, (entire surface ground 2948 — 
Smooth opal - - - - 52:68... 
Ground opal, - - - - - - + 55.85 E 
Ground opal, ornamented with painted figures, 
the figures intervening between the burner AB OB). goar 
and the photometer screen, 
It should be mentioned in passing that Verver* had previously called 
ry ound 
the light which is produced. This loss (déperdition) was shown by the 
following experiment. A burner with twelve jets without any chimney 
afforded an illuminating power of 6°75 candles ; but on surrounding the 
wick with a clean and perfectly polished chimney, the illuminating power 
amounted only to 5°25 candles ; it had consequently diminished 1:50 can- 
dles, é. e., 22 per cent.” But, as Schillingt has already remarked, this 
experiment alone does not prove that the whole of the lost 22 per cent 
was absorbed by the glass of the chimney, since the conditions under 
which the gas is consumed when a chimney Is used must be entirely dif- 
ferent from those which obtain when no chimney is employed. age 
_ Immediately after the arrival in this country of the journal containing 
Mr. King’s note, I was requested by Mr. W. W. Greenough, Agent of 
the Boston Gas Light Co., to institute a series of comparative experiments 
upon this subject. Since the results of these experiments have in the 
main fully corroborated those of Mr, King it seems but just to this gen- 
blicity. ; 
heets of glass (ordinary window panes) 
Make i Runs ee the \ ae aA toa rack of blackened 
wire which was fastened to the photometer bar (100 inches long) at a dis- 
The gas employed was prepared, from 
expressly for these experiments an 
U . 
tas ’ bonne et L’Eclairage au Gas Le Prince, 
Pepa oe Gas d Law 4 orver, Prof. de Ohimie et de Physique a 0 Ath- 
; ide, 1858, p. 26. nee 
oy Royale oe ee Laaokate, Me Miinchen, 1859, ii, 877. 
t Itd ot appear that the distance from the source of light at which the glass 
eereen t ne pk i appreciable influence upon the amount of light transmitted 
by it at all events no such influence could be detected in a number of experi- 
ments made purposely to test this question. 
