54 W. Brande's Lecture on some 
other, with a small table between them, as represented in the 
annexed drawing. (PL II.) 
When it was necessary to ascertain the relative tempera- 
tures of the balls with accuracy, I made use of the instrument, 
jig. 2, devised by Mr. Pepys, in which a a represent two thin 
spheres of brass containing delicate thermometers, the bulbs 
of which, as well as the interior of the spheres, were coated 
with lamp black, to render the increase of temperature more 
evident. One of the balls w^as connected with the negative, 
the other with the positive conductor of a small electrical 
machine of Mr. Nairne's construction, as represented in 
fig- 1) so that the apparatus was perfectly insulated. 
§. III. 
Exp. 1. A small stream of olefiant gas was burned between 
the balls. The flame was evidently attracted tow^ards the 
negative side. The combustion was continued for one minute. 
At the commencement of the experiment, the mercury in the 
thermometers stood at 6o° Fahrenheit ; at its termination 
the positive thermometer indicated 62®, the negative 72*. 
2. The experiment was repeated with sulphuretted hydro- 
gen : the flame w^as now only slightly attracted by the nega- 
tive ball, but the sulphureous acid vapour passed off tow^ards 
the positive surface. . 
In this experiment the positive thermometer rose 3®, and 
the negative thermometer 6° in one minute. 
3. A very small flame of phosphuretted hydrogen was 
slightly bent towards the positive pole. In one minute it 
produced an effect upon the positive thermometer = 5", upon 
the negative = 3°. When a larger flame was used, it 
