ARTIFICIAL ILLUMINATION. 167 
light is produced by conducting the air supply to the flame through 
the heated body of the lamp as in the ordinary regenerative gas system. 
Of course it is obvious that, as the oil falls in the receiver, the diminu- 
tion of the pressure head will cause a less and less rapid flow of oil, 
aud we might expect the flames gradually to diminish in size. 
This does happen, but to a small extent only, because the receiver, as 
you see, is of large area, but of very small depth. Some little care, of 
course, must be given to the adjustment of the flames, but I have found 
no practical difficulty at present and can only regard the lamp as one 
promising to be of value in careful hands, at any rate, where gas can- 
not be obtained. 
I now propose to ask your consideration of some figures which will 
indicate the efficiencies of the various systems of lighting and their 
comparative economies. I may mention that the tables which I pro- 
pose to show you represent the results of careful and prolonged tests 
made by myself, and for which I take the entire responsibility. 
(1.) I will call your attention to what is now on the screen, showing 
you the efficiency of the various gas burners :—- 
Hrricrency oF vARIouS Gas Burners. 
Sanat Candles) Cube eater Ga | Canes pe ei 
Common “Bray” No.2... ... 3 3 il 
» » » 5 9 6 Tb 
* Fe a! 14 a 2 
BraysseSpecialeqiNow eee se 20 8 2:5 
Sion Coney Acr oad amet eneen ean 16 5 3°2 
““Wenham” Regenerating ... ... 67 ll 61 
No. 2. Tested at 45° 
DW O= (8 AiO 1 eee mer mnets. Unie 20 3 6°6 
*Welsbach ” Incandescent ..._ .. 48°2 3°8 12°7 
ee ice ae SA) annobut udm 
Without alluding to each item, I may remark that the figures show 
as I have before pointed out, that small open burners are unprofitable the 
common “ Bray” No. 2 giving an efficiency of only 1 candle per cubic 
foot of London gas burnt per hour, while the best form of a “ Bray ” 
burner is credited with 24. Notice also, please, that the regenerative 
system, illustrated by a No. 2 lamp tested at 45°, gives an efficiency of 
about 6°1 candles, which may be taken asa good all-round value. The 
Welsbach incandescent burner gives, as you see, an efficiency of 12:7. 
This is the average result of a large number of mantles tested and 
