220 Prof. Draper’s ption of the Tithonometer. 
tains them, at a distance of several inches, there is no difficulty — 
in understanding why a similar effect should take place witha — 
violent explosian when the discharge i is made through their midst; 
nor how a great many mixtures may be made to unite under the : 
Same treatment. A flash of lightning cannot take place, nor an — 
electric spark be discharged, without chemical charges being 
itted.* | 
its Chidigiaions are ony proportional to the auet ties 0 gi jem q 
incident on it. ea 
As it is necessary, owing to the variable force of daylight, to” 
resort to artificial means of illumination, it will be found advan- 
tageous to employ the following method of obtaining a flame of — 
suitable intensity. 
Let A B, fig. 4, be an Argand oil-lamp, of which the wick is C. — 
Over the wick, at a distance of half an inch or thereabouts, place — 
a plate of thin sheet copper, three inches in diameter, perforated 
in its centre with a circular hole of the same diameter as the wick, — 
and concentric therewith. This piece of copper is represented at _ 
dd; it should have some contrivance for raising or depressing it — 
through a small space, the proper height being determined by 
trial. On this plate, the glass cylinder e, an inch and three quar- 
ters in diameter and eight or ten inches long, rests. 
When the lamp is lighted, provided the distance between the — 
plate dd and the top of the wick is properly adjusted, on putting 
on the glass cylinder the flame instantly assumes an intense 
whiteness; by raising the wick it may be elongated to six inches 
or more, and becomes exceedingly brilliant. Lamps constructed — 
on these principles may be purchased in the shops. Ihave, how- — 
ever, contented myself with using a common Argand study-lamp, 7 
supporting the perforated plate dd at a proper altitude by a retort a 
* Sincé the above was printed in London, [ have found that there is no difficulty 
in making chlorine and hydrogen explod 5 ty passing the spark from a den jar 
of the capacity of a quart, outside the sealdand tube of the instrument. This result 
therefore confirms the views here expressed, that combinations ensuing on the pas- 
f an electric spark are not entirely due to any such mechanical agency as 
condensation or percussion, but to the action of the radiant matter emitted. I be- 
lieve it will be found, that the explosive union of oxygen and hydrogen a an elec- 
tric discharge is a phenomenén of the same kind. 
