180 Mr J. Monckman, On the arrangement of electrified [Jan 80, 
dipped into nitrate of silver and exposed to light and the fumes 
of phosphorus to render it a good conductor of electricity. 
To prevent a flow of electricity from the matches to the ball 
the ends are covered with wax. It is essential that all the 
matches rise to the same height above the surface of the water or 
the larger ones force their way to the centre and spoil the figures. 
To achieve this the weight of the pin and disc must be very 
carefully adjusted by cutting the lead if too heavy and by adding 
white lead if too light. 
Two large Leyden jars were introduced into the circuit to 
prevent the charge falling too quickly when the print was being 
taken. 
I found that the best method of printing was to cover one 
end of a long strip of glass with dilute printer’s ink and touch 
the top of each match with it. When the whole had assumed 
the proper figure, a sheet of glass was slipped in between the 
ball and the floats and gently lowered until good contact was 
made, after which it was transferred to paper. 
The figures obtained are shewn in the diagram and are placed 
so that the line of symmetry is vertical. (Figures to which M 
is put were produced by an electromagnet only.) 
The next experiment was to repeat A. M. Mayer’s experiment 
with magnets floating on water (American Journal of Science and 
Art, 1878, 3 Series, V. XVL, page 247), in order to compare the two 
sets of figures. The figures obtained varied somewhat from his. 
This is caused by the change of distance of the attracting magnet. 
Thus with eight floating magnets a very small attracting magnet 
gave three in the centre and five outside, a larger one gave 
figure 86, and a larger still further removed again fig. 8a. 
Others vary in the same way. 
In order to get a more even field Prof. Thomson proposed 
to use a large electromagnet. This being placed at a distance of 
about two feet caused several changes in the combinations. 
The figures were more regular than those given by the 
electrified floats. I did not however consider it necessary to print 
them when they produced the same forms. 
4 to 9 magnets gave 4 to 9 (in fig. 2),8 gave 8a, 9 and 10, 
9, 10a, 106, 11 gave lla, 12, 12a and M12, 13 and 14 gave 13 and 
14 and 15,150, 18 and 20 gave 18 and 20, but 16, 17, and 19 gave 
M16, M17 and M19. 
In some of the higher numbers a tendency to set themselves 
in hexagons with one in the centre was observed, and as this is 
the figure in which the force on each magnet is equal, it appeared 
probable that with an even magnetic field and an infinite number 
of floating magnets the whole would be thus distributed. To 
test this forty-eight needles were prepared and placed upon the 
