OF ALL THE PHENOMENA OF TERRESTRIAL MAGNETISM. 
107 
said the small needle employed for exhibiting- the effects; and even this, but for 
its necessary minuteness, might be replaced by a galvanic needle on M. Am- 
pere’s construction. At the same time, I must beg again to observe, that it 
follows from the laws obtained by M. Biot, that no position of a single magnet, 
nor the arrangement of any numbers of such bodies within the globe, could by 
possibility exhibit the same phenomena, particularly as relates to the intensity 
of the needle. 
I am quite aware that, after all, this does not amount to a demonstration 
that the magnetic phenomena of the earth are produced only by electricity ; 
yet seeing as we do, in every operation of natural effects with which we are 
acquainted, that the agents employed are not more numerous than necessary, 
it will perhaps be admitted that I have at least shown the high probability that 
all terrestrial magnetic phenomena are due to some particular modification of 
electricity, and that magnetism, as a distinct quality, has no real existence in 
nature. 
It is true, that as far as the discovery of Mr. Oersted goes, we have no idea 
how such a system of currents can have existence on the earth, because, to 
produce them, we have been obliged to employ a particular arrangement of 
metals, acids, and conductors ; but, fortunately, a subsequent step, not less im- 
portant than the former, was made by Professor Seebeck of Berlin, who dis- 
covered that the mere application of heat to a circuit composed of two metals, 
was competent to produce the same development of galvanic and magnetic 
effects as those above described; and there can be no doubt, that if the con- 
ducting wire of the globe I have described, were removed, and each parallel 
made complete in two metals, that all the phenomena it now exhibits by aid 
of the galvanic battery might be represented by the application of heat only. 
The effect of heat is so obvious in the production of magnetic developments, 
that I have seen a rectangular circuit on Professor Seebeck’s principle, con- 
structed by Messrs. Watkins and Hill, which, by the momentary application 
of a spirit lamp, became sufficiently magnetic to deflect the needle several de- 
grees, and even the minute change of temperature that could be produced by 
contact with the hand, exhibited a sensible effect : this circuit, however, was 
formed of two metals as proposed by Professor Seebeck ; but Mr. Sturgeon of 
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