1819.) © Scientific Writings of Dr. Ingenhousz. 83 
iron with which that metal is alloyed. Platinum in a state of 
purity is not in the least attracted by the magnet. 
3. A ready Way of lighting a Candle by a very moderate 
Electrical Spark. Phil. Trans. 1778, p. 1022.—Dr. Ingenhousz, 
if we are to form our opinion of him from his writings, seems to 
have been rather attached to parade and show, and probably 
took great delight in exhibiting brilliant experiments to others. 
Some of the most showy experiments (if they be entitled to the 
name), still exhibited in chemical lectures, were contrived by 
him; such as the combustion of iron wire, of camphor, and of 
phosphorus in oxygen gas, and the inflammable air pistol by 
means of common air and ether. The experiment described in. 
this paper may, perhaps, without much impropriety, be classed 
along with those just mentioned. He kept by him a ready 
charged Leyden jar, the knob, of which was bent a little so as 
rather to hang over the jar. He had likewise an assortment of 
brass wires of the requisite length with a little cotton tied loosely 
at one end of each. This cotton was dipped into finely powdered 
resin. One end of the wire being brought in contact with the 
outside coating of the jar, the other extremity to which: the 
cotton was attached was brought near the knob. A spark was 
discharged, which set fire to the cotton, and by means of this 
flame, which lasted about half a minute, it was easy to light a 
candle. 
4. Electrical Experiments to explain how far the Phenomena 
of the Electrophorus may be accounted for by Dr. Franklin’s 
Lheory of Positive and Negative Electricity. Phil. Trans. 1778, 
p- 1027.—This is, perhaps, the most valuable of all the scientific 
papers of Dr. Ingenhousz inserted in the Phil. Trans. It 
explains the phenomena of the electrophorus in a very clear and 
satisfactory manner. The electrophorus is a very curious and 
useful instrument, invented by Volta. It consists essentially of 
a cake of resin covered with a plate of metal, moveable at plea- 
sure by means of a glass handle attached to it. When the cake of 
resin has been charged with electricity by means of a Leyden 
jar, if you put the metallic plate over it, and while in that posi- 
tion touch the upper part of the plate with your finger, on liftin 
je the plate by means of its glass handle, it will be foun 
charged with the opposite kind of electricity of the resinous 
cake, and will give a spark to any conductor brought into its 
neighbourhood ; and this experiment may be repeated at plea- 
sure for months together without any renewal of the charge of 
the resinous plate. 
Dr. Ingenhousz’s explanation depends upon two principles, 
which, he says (at least the first of them), had not been attended 
to before his time. These principles are the following: 1. Elec- 
trical bodies do not easily receive an electrical charge; but 
when once charged, they are not easily deprived of the electri- 
city thus communicated. The consequence is, that they in 
F 2 
