One of the most impudent of these quacks was named Benjamin Douglas Perkins, whose father claimed to be the inventor of the metallic tractors, which were rods made either of a combination of copper, zinc, and gold, or of iron, silver, and platinum, and he explains, in the specification to his patent, that ‘the point of the instrument thus formed, I apply to those parts of the body which are affected with diseases, and draw them off on the skin, to a distance from the complaint, and usually towards the extremities.’ He charged the moderate sum of five guineas a set for these precious instruments, and made a good thing out of them. He was a member of the Society of Friends, and, as a proof that his charlatanism was believed in, this benevolent society subscribed largely, and built for him the _Perkinean Institution_, an hospital where the poor could be treated on his system, free of cost. He was an adept in the art of puffing, and his ‘Testimonials’ are quite equal to those of modern times. I will only cite two. ‘My little infant child was _scalded_ with hot tea on the forehead, about three and a half inches in length, and three-fourths of an inch in breadth, which raised a vesicle before I had time to apply anything to it. The _Tractors_ were solely used, and the whole redness disappeared. The Blister broke, &c.’ ‘A lady fell from her horse, and _dislocated_ her ancle, which remained several hours before it was reduced, by which it became very much _swelled_, _inflamed_, and _painful_. Two or three applications of the _Tractor_ relieved the pain, and in a day or two she walked the house, and had no further complaint.’ Then also was Dominicetti, who, in 1765, established a house in Cheyne Walk, Chelsea, for medicated baths, but he hardly belongs to the magnetisers. Then there was Katterfelto, but he, too, hovers on the borderland of quackism--vide the following one of hundreds of advertisements.[102] ‘By particular Desire of many of the First Nobility. This PRESENT EVENING and TO-MORROW, At late COX’S MUSEUM, Spring Gardens, A SON of the late Colonel KATTERFELTO of the Death’s Head Hussars, belonging to the King of Prussia, is to exhibit the same variety of Performances as he did exhibit on Wednesday the 13th of March, before many Foreign Ministers, with great applause. MR. KATTERFELTO Has had the honour in his travels to exhibit before the Empress of Russia, the Queen of Hungary, the Kings of Prussia, Sweden, Denmark, and Poland. MR. KATTERFELTO’S Lectures are Philosophical, Mathematical, Optical, Magnetical, Electrical, Physical, Chymical, Pneumatic, Hydraulic, Hydrostatic, Styangraphic, Palenchic, and Caprimantic Art. MR. KATTERFELTO Will deliver a different Lecture every night in the week, and show various uncommon experiments, and his apparatus are very numerous, and elegantly finished: all are on the newest construction, many of which are not to be equalled in Europe. MR. KATTERFELTO