296 Miscellaneous Intelligence. 
Until the commencement of the present century artificial light was 
derived almost exclusively from the animal kingdom; but the great 
economy attending its immediate production from our vast stores of 
vegetable fuel is becoming more and more apparent, and is in fact so 
generally admitted, as to render more than a mere allusion to it anda 
glance at the following Table, unnecessary. 
TasLE—showing the comparative cost of light from various sources, 
gs equal to 20 sperm candles burning 120 grains per hour each, 
or 10 hours 
HAH 
Wax, weg iis er eaeeven “to esis at 1Qb 
Spermaceti, . ooseoe ‘ wi . 6 8 
Tallow . . ‘ ‘ . . 2 8 
Sperm oil (Carcel’s Lamp), me ate 1 10 
ndon gases, B, C, D, E,* - : ° 0 44 
Manchester gas, - * . * . o 2 
London gas, A, - - : i 0 24 
We will therefore confine our attention principally to the light pro- 
duced from vegetable fuel, in considering the economical and sanatory 
bearings of artificial light. 
temperature shown to be inadequate to the ignition or even scorching 
of the finest cambric or gun cotton.) Usually, however, solids require 
a temperature of or 700° F. to render them luminous in the dark, 
and must be heated to 1000° F. before their luminosity becomes visible 
in daylight. Liquids require about the same temperature. But to ren- 
der gases luminous, they must be exposed to an immensely higher tem- . 
erature ; even the intense heat generated by the oxy-hydrogen blow- 
pipe scarcely suffices to render the aqueous vapor produced visibly lumin- 
ous, although solids, such as lime, emit light of the most dazzling splen- 
dor when they are heated in this flame. Hence, those gases and va- 
hydrogen are the only ones capable of practical application: these lat- 

(i oa 
* London gases, A, B, 0, D, E—These are the gases furnished to consumers bys 
five of the principal London Companies. For obvious reasons the names of the 
