It was particularly in September and October, 1837, that several parties attached to scientific pursuits in Liverpool, were engaged in repeating the experiments of Dr. Golding Bird, published in the Phil. Trans. for 1837, and of which he gave an account before the chemical section of the British Association at its meeting in Liverpool, over which Dr. Faraday presided. The apparatus used on that occasion by myself and others, was precisely that recommended by Dr. Bird, consisting simply of any glass vessel A, capable of holding a solution of common salt, into which is inserted a gas-lamp chimney, having its lower end plugged up by pouring into it plaster of Paris D; a solution of sulphate of copper is then poured into it, and the whole immersed in the contents of the glass A, and tightened with pieces of cork a, a, a; C is the copper, and Z the zinc plate. The result expected from this arrangement was the deposit of metallic veins of copper within the plaster diaphragm, independent of any connexion with the poles of the battery. Dr. Faraday and every other electrician expressed surprise and doubts at the results in this respect, said to have been obtained by Dr. Bird, and Dr. Faraday particularly urged the necessity and importance of caution in receiving as established a result so greatly at variance with all former experience, and proceeded to explain a variety of causes tending to lead to fallacious results in this curious and interesting experiment.

I have still by me the crystals of copper obtained by myself in my first experiments in September, 1837. I was at that time a good deal in communication with Mr. John Dancer, philosophical instrument maker, Liverpool (now of the firm of Messrs. Abraham and Dancer, Manchester), and this was a frequent subject of conversation. It was about October of the year following (1838), that Dr. Brett was delivering lectures on electricity and galvanism at the Medical Institution, Liverpool, and being in communication with Mr. Dancer respecting the apparatus for those lectures, I was arranging for a supply of galvanic troughs, when Mr. Dancer showed me a ribbon of copper, thin but very firm, granular on one side, while it was bright, and smooth, all but some raised lines, on the other. Seeing my curiosity a good deal excited, he said at once, it was the result of galvanic action, and explained the whole process. He particularly noticed that generally the deposit was more crystalline, granular, and brittle. The difference of the specimen I was examining, which possessed all the tenacity of rolled copper, he attributed to his having gone to the potteries to look out suitable jars for forming sustaining batteries, and having fixed on a lot which he was told would not answer, as they were not glazed, and would not hold liquor. The idea immediately occurred to him that such unglazed jars might be turned to account and used instead of bladder, brown paper, plaster of Paris, and other porous sub

stances he had previously employed. He, therefore, immediately obtained a sample for experiment, and the result was a more firm and compact deposition of copper, though that was not what he was seeking, his object being durability and equable action. But Mr. Dancer was not negligent of the accidental discovery of a deposit possessing such tenacity as belonged to the copper resulting from batteries, in which he employed porous earthenware; neither did he make any secret whatever of the occurrence. A specimen of the copper he obtained by that process was shown by me the same day to Dr. Brett, in the laboratory of the Apothecaries' Hall, Liverpool, who was equally unable with myself to guess the mode by which it had been obtained. When informed of the process, he was much gratified by the statement.

These facts were named by Mr. Dancer's friends to various persons, and in my capacity of Honorary Secretary, at the time, of a Literary and Scientific Institution, this curious electrical experiment of Mr. Dancer's was frequently a subject of conversation.

Subsequently, Mr. Spencer laid claim to the discovery of the means for obtaining metallic casts by galvanic agency, and having, with others, expressed doubts of Mr. Spencer's claim to priority, I was surprised when verbally informed by Mr. Spencer, that I was quite in error in repeating such statements, and that so far from its being the fact, Mr. Dancer had "made the amende honorable." This statement, which appeared to me a

very extraordinary one, induced me to write a note of inquiry to Mr. Dancer, and the following is his reply :

"21, Pleasant Street,

Liverpool, 17th June, 1840.

"DEAR SIR-Since I saw you I have scarcely had ten minutes to spare, and at present I have not time to enter fully into detail. With respect to the precipitation of copper for the purpose of obtaining an impression, I give you the following account (part of which I believe you were aware of in 1838), and is, in fact, the substance of a letter written by me in reply to Mr. T. Spencer. I stated that I had been engaged, in connexion with Mr. Unsworth, in experiments with batteries of various constructions, previous to my acquaintance with Mr. Spencer, and I had used various porous substances in my batteries (which were those excited with common salt and sulphate of copper). To prevent the intermixture of the solutions-in one I had used a thin plaster division, and I obtained a very compact deposition of metallic (copper) on the copper plate of my battery, which I pulled off. I recollect Mr. Unsworth and I talking of it as one method of multiplying our battery plates, while we were making use of the battery. From this I was led to try if I could precipitate a larger and more uniform plate, and I succeeded in doing so. I afterwards thought that unglazed jars, such as I could obtain at the Pottery, would be more durable for the