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obtained from a magneto-electric coil when short, and the shock 
when it is long.’’ 
Many other ingenious instruments were constructed by Saxton 
while he was connected with the Adelaide Gallery. He made the 
apparatus with which Wheatstone’s celebrated experiment of meas- 
uring the speed of electric transfer through a wire was performed, 
by which was established the fact that this transfer requires time for 
its accomplishment. He constructed for the Gallery a compound 
steel magnet which sustained the weight of five hundred and twenty- 
five pounds; and also a magnetic needle several feet in length, hav- 
ing a mirror on its end, by which he exhibited for the first time on 
a magnificent scale the daily and hourly variations of the magnetic 
force of the earth by the movements of a reflected beam of light. 
This use of the mirror, however, he -had made use of as early as 
1825, thus anticipating the similar application made by Ganss. One 
modification of the revolving mirror thus early used by Saxton con- 
sisted in fastening a small mirror to a rotating axis obliquely, so 
that when a beam of light was thrown upon the mirror, and suff- 
cient speed given to it, a large circle of light would be projected on 
the ceiling. When, by a powerful train of wheel work, very rapid 
rotation was produced, any fluctuations taking place in the inten- 
sity of the light could at once be detected. He showed, for exam- 
ple, that when the light came from charcoal points forming the 
poles of a voltaic battery, the circle of light exhibited a mottled or 
dotted appearance, indicating a rapid alternation of intensity in 
the electrical discharge. 
In a diary kept by him during his residence in London, he gives 
‘‘a method of determining the position of the interior magnetic 
poles of the earth by projecting, in the form of a large circle, a 
section of the earth through the magnetic meridian. On the cir- 
cumference of this drawing he next projected the dip of the needle 
in different latitudes from the equator to the pole, and by prolong- 
ing these projections until they meet in the interior of the earth, 
determining the positions of the centres of magnetic influence in 
the two hemispheres. By this process he arrived at the conclusion 
that the magnetic polarity of the earth is deeply seated in the in- 
terior, and that consequently the magnetism of the globe may be 
represented by a comparatively short magnet, the axis of which 
passes through the centre of the globe.’’ Moreover, he made ‘‘a 
drawing of an arrangement of apparatus for obtaining an electrical 
