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MAY, 1842.


(Continued from page 231.)


The Large Silver Medal and Thirty Guineas were this session pre

sented to Mr. W. STURGEON, 8, Artillery-place, Woolwich, for his Improved Electro-Magnetic Apparatus. ^ A set of which has been placed in the Society's Repository.*

MR. Marsh's apparatus, for the same purpose as Mr. Sturgeon's, was rewarded by the society in the session before last. The battery, consisting of plates presenting eight surfaces of about a square foot each, and weighing from twelve to thirteen pounds, was the smallest that had at that time been applied to electro-magnetic researches. The rest of his apparatus, with few exceptions, was such as had already been used by Ampére, Sir H. Davy, Mr. Barlow, Mr. Faraday, and others, fitted together in a very convenient way, and stowed in a box, which, with the battery, made a package sufficiently portable.

Mr. Sturgeon's apparatus is even more portable than Mr. Marsh's, and (the moving parts being at the same time larger) is better fitted than that for the use of the lecturer.

The battery is similar in construction to Professor Hare's calorimotor, and consists of two fixed, hollow, concentric cylinders of thin copper, having a moveable cylinder of zinc placed between them. Its superficial area is only 130 square inches, and it weighs no more than llb. 5 oz. It is moveable on an upright metallic rod, like a laboratory lamp, and may therefore be adjusted to any convenient height. It will not hold more than about a pint of

• Extracted from the Transactions of the Society of Arts, for 1825. Ann. of Elec. Vol. VIII, No. 47. May, 1842.

liquid, which should be composed of one part nitric acid, and eleven parts water: it is charged with the greatest ease, by merely pouring in the liquor from a common lipped jug. A farther advantage of the construction is, that after every experiment the liquor may be returned to the jug, while preparations are making for the next, by which the battery, when wanted, is in a state of high activity, and is undergoing no deterioration in the interval between one experiment and another.

A farther point of novelty is, that Mr. Sturgeon has very judiciously chosen to have a small galvanic power, assisted by a strong magnetic power, rather than the reverse, as is usually the

This has enabled him greatly to economise in the size of his battery, and in the cost of acid to excite it, while the increased magnetic power is obtained at a small first expense, and needs no renewing.


Letter to the Secretary of the Society of Arts. Sir,

No, 9, Artillery-place, Woolwich. The science of electro-magnetism, although so generally interesting, yet (comparatively speaking) appears to be very little understood. This latter circumstance is probably, in a great measure, owing to the difficulty of making the experiments, and the great expense attending the process; for, besides the first price of a large battery, considerable expense in acid must always attend its excitation, whenever an experiment is attempted. Large batteries are always attended with difficulty of management, and the great quantity of hydrogen evolved during the process renders the use of them extremely inconvenient to the operator. These are evidently great obstacles to the experiments being often repeated, and to the science being generally known. Another, and perhaps no less obstacle to the advancement of this interesting science, is, that the experiments being hitherto exhibited on so small a scale, are by no means calculated to illustrate the subject in public lectures ; for when the experimenter succeeds even io his wishes (which is not frequently the case), the experiment can only be seen by a very near observer, and the more distant part of the auditory are obliged to take for granted what they hear reported (from those persons who are more favourably situated), of some of the most interesting facts, which they, from their distance, are unable to witness.

With a view of removing, in some measure, these apparently formidable obstacles in the progress of this infant science, I have devoted a considerable portion of time, labour, and expense, in repeating several of the experiments, under various circumstances, and with various forms and sizes of batteries. I have likewise instituted a series of experiments, for the purpose of discovering, if possible, if any particular ratio of galvanic and magnetic power was

absolutely necessary to be observed in the process of electromagnetism. If no particular proportion of those two powers was essential, then it appeared highly probable that an increase of magnetic power might compensate for a deficiency of the galvanic, and thereby render the use of large galvanic batteries quite unnecessary, an object which I considered both interesting in its nature, and, by reducing the expense, and facilitating the process, exceedingly desirable to the experimenter; and I am happy to state, that my labours were no ways abortive, for instead of electro-magnetic phenomena depending on powerful galvanic, and feeble magnetic force, as had till then been practised, I found, during that inquiry, that the galvanic force may be reduced to almost any degree, provided the magnetic be sufficiently powerful. This discovery led me to the use of powerful magnets, and small galvanic batteries, for with small magnets the experiments can never be made on a large scale, although the galvanic force be ever so powerful; and as minute and delicate experiments are not calculated for sufficiently conspicuous illustration in public lectures, I considered that an apparatus for exhibiting the experiments on a large scale, and with easy management, would not only be well adapted to the lecture room, but absolutely valuable to the advancement of the science. Upon this principle I have constructed a complete set of instruments, which, from their superior magnitude, and peculiar arrangement, in my humble opinion, and by the certificates I have been honoured with, are, in the opinion of gentlemen whose judgment I presume will ever be held in the highest estimation, well adapted for the illustration of the subject, either in the private study or public lecture room.

It will be understood from what I have already stated, as well as from an inspection of the instruments, that the mode which I have taken for the production of electro-magnetic phenomena is more simple in its management, less expensive in the process, better calculated for the illustration of the subject, and the reverse of that which has hitherto been used, and which, by its almost entire dependence on the tedious and expensive process of galvanism, has considerably retarded and obscured this new and interesting science; for whenever an experiment was not attended with the anticipated success, the failure was generally attributed to an insufficiency of galvanic power; and in order to increase the effect, it the experimenter had no other means of accomplishing his object, than by augmenting the power of his battery, or by reducing the size and increasing the delicacy of his other apparatus, the magnetic power being either entirely lost sight of, or regardlessly neglected, as if no ways materially concerned in the process.

I have found, however, by the above-mentioned course of experiments, that the magnetic force is as essential as that of galvanism to the development of electro-magnetic phenomena ; and the apparatus which I now submit to the attention and impartial consideration of

appears that

your valuable society, acting on the principle of powerful magnetism
and feeble galvanism, will, I trust, be found more eligible and efficient
than any other that has yet been brought before the public.
A. Aikin, Esq.

I am, Sir, &c., &c., &c.,
Secretary, fc., fc.



Royal Military Academy, Woolwich Common, Sir,

9th May, 1825. As I understand that Mr. William Sturgeon proposes to submit his galvanic battery and electro-magnetic apparatus to the consideration of the Society for the Encouragement of Arts, &c., I take the liberty of recommending them to your favourable consideration, although I have not the honour of being personally known to you. Since the first discovery of the action of the galvanic circuit on the magnetic needle, I have witnessed all the principal phenomena connected with electro-magnetism as exhibited by batteries and apparatuses of different constructions, and have no hesitation in saying that the battery and apparatus of Mr. Sturgeon are most admirably calculated for exhibiting all these phenomena in the most striking manner, and that they afford peculiar facilities for investigation in this most interesting science. The expense attending the purchase and use of large galvanic batteries, the difficulty of keeping them in powerful action, and the inconvenience of using them, except in laboratories, must all tend to retard the progress of a science, which has opened a new field for inquiry ; and as the battery and apparatus of Mr. Sturgeon are free from all these objections, I consider that, by rendering them public, the cause of science is promoted, and that he is deserving of every encouragement for their invention and successful application.

I am, Sir, A. Aikin, Esq.,

&c., &c., &c. Secretary, foc., fc.

S. H. Christie, M.A.

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Royal Military Academy, Woolwich,

May 9th, 1825. I beg leave to introduce to the favourable notice of the society, Mr. William Sturgeon, a resident of this town, who has for some time devoted himself most sedulously to the improvement of apparatus for the development and exhibition of the properties of electromagnetism. He wishes to solicit the patronage of your valuable institution to a new battery of his invention, which, while it is very far smaller than any other of which I have heard, is very efficacious, and at the same time remarkably calculated to facilitate the experiments. Mr. Sturgeon has also, in my judgment, greatly improved several other classes of apparatus employed in this interesting de

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