The phenomena apparently produced by these instruments were astounding, and misled every observer of them; until Dr. Haygarth of Bath proved by a process to which objections was impossible, that they were referable not to metal points, but to the mental condition of those who used them. "Robert Thomas," says Dr. Haygarth in his interesting work, "aged forty-three, who had been for some time under the care of Dr. Lovell, in the Bristol Infirmary, with a rheumatic affection of the shoulder, which rendered his arm perfectly useless, was pointed out as a proper object of trial by Mr. J. W. Dyer, apothecary to the house. Tuesday, April 19th, having everything in readiness, I passed through the ward, and, in a way that he might suspect nothing, questioned him respecting his complaint. I then told him that I had an instrument in my pocket which had been very serviceable to many in his state; and when I had explained to him how simple it was, he consented to undergo the operation. In six minutes no other effect was produced than a warmth upon the skin, and I feared that this _coup d'essai_ had failed. The next day, however, he told me that 'he had received so much benefit that it had enabled him to lift his hand from his knee, which he had in vain several times attempted on Monday evening, as the whole ward witnessed.' The tractors I used being made of lead, I thought it advisable to lay them aside, lest, being metallic points, the proof against the fraud might be less complete. Thus much, however, was proved, that the patent tractors possessed no specific power independent of simple metals. Two pieces of wood, properly shaped and painted, were next made use of; and in order to add solemnity to the farce, Mr. Barton held in his hand a stop-watch, whilst Mr. Lax minuted the effects produced. In four minutes the man raised his hand several inches; and he had lost also the pain in his shoulder, usually experienced when attempting to lift anything. He continued to undergo the operation daily, and with progressive good effect; for on the twenty-fifth he could touch the mantel-piece. On the twenty-seventh, in the presence of Dr. Lovell and Mr. J. P. Noble, two common iron nails, disguised with sealing-wax, were substituted for the pieces of mahogany before used. In three minutes he felt something moving from his arm to his hand, and soon after he touched the board of rules which hung a foot above the fire-place. This patient at length so far recovered that he could carry coals and use his arm sufficiently to help the nurse; yet, previous to the use of the spurious tractors, he could no more lift his hand from his knee than if a hundredweight were upon it, or a nail driven through it--as he declared in the presence of several gentlemen, whose names I shall have frequent occasion to mention. The fame of this case brought applications in abundance; indeed, it must be confessed that it was more than sufficient to act upon weak minds,