A SPRING CRUTCH. 



147 



HINTS ON VARIOUS MODES OF PRINTING 



FROM AUTOGRAPHS. 

 Bt G. CuMBERiAVB, Esa. — Phil. Journ. No. 126. 



After some remarks on the advantage 

 which would result to authors from the 

 invention of a mode of issuing their works 

 to the public without the intervention of 

 a publisher, and of taking off the copies 

 as they were wanted ; M. G. enumerates 

 several kinds of materials which he con- 

 ceives to be best adapted for accomplish- 

 ing the purpose. 



The first of these which was suggested 

 to him was copper, to be written upon 

 by a style through white wax : but this 

 could only be adopted for small pieces. 

 He next supposes a kind of copper or 

 brass latten, to be rolled very thin, and 

 written upon with very corrosive ink, 

 which would soon eat through the plate, 

 and thus produce a stencil by which the 

 printing might be effected. 



If capital letters only were used, a 



1 paper stencil might be made by means 

 of punches, which would last as long as 



' the metal one ; as many thousand im- 



i pressions have been taken from a stencil 

 made of oiled paper. Tinfoil or bismuth 



I might also be used for the same purpose. 

 Pannels of wood covered with plaster of 

 Paris are suggested for drawings ; and it 

 is added that good impressions liave been 

 obtained from small blocks of this sub- 

 stance. It is also imagined that diagrams 

 or plans might be obtained from a smooth 

 board covered with thick paper and cut in 

 relief. 



Pontipool ware (pewter and copper co- 

 vered with wax) ma)"^ easily be engraved 

 upon with a style ; and pencil drawings 

 readily engraved in this manner. 



If a material could be found that resists 

 the action of fire, it is supposed that we 

 might write with it upon blocks of wood, 

 and char the rest a little way in, so as to 

 leave a projecting letter. Glass, turtle-) 

 shell, silver, &c. are mentioned as sus- 

 ceptible of being etched upon ; and 

 M. G. likewise thinks "that if we could 

 write upon a block of stone, or plate of 

 glass, with an ink so thick as to leave the 

 words in relief we might, by pressing 

 putty on it, take a cast sufficiently durable 

 to make many impressions, or thus cast 

 it in plaster of Paris from the relievo on 



the smooth block, but this would print 

 the words white on a black ground. This 

 writer likewise remarks that a volute 

 shell, ground down on a hone, is the 

 most secure stamp or seal for prints, 

 drawings, and similar property. 



Retrospect. 



A SPRING CRUTCH. 



By Mr. George Prislet. — Church Street, Soho. — 

 Trans. Society of Arts. Vol. 28. 



The head of the crutch is fixed upon a 

 short brass tube, which is fitted to slide 

 in another, fastened upon the top of the 

 crutch staff; within this tube an helical 

 (spiral) spring is concealed, that supports 

 the head of the crutch, which yielding in 

 a certain degree to the pressure, prevents 

 the shocks which common crutches occa- 

 sion, and enables the person who uses 

 crutches of this kind to move quicker 

 and with less fatigue. 



For the convenience of package, the 

 staff of the crutch is made to divide in 

 two parts, which put together in a brass 

 tube, where a spring that presses against 

 the inside of the tube, prevents any 

 danger of their separating by accident. 



The silver medal was given to Mr. 

 Prisley for his contrivance by the Society 

 of Arts. 



Observations. — This instrument pro- 

 mises to be of great assistance to lauie 

 people ; and is the more likely to be 

 advantageous, from its imitating tlie 

 mechanism of nature, which in the 

 animal frame interposes elastic cartilages, 

 that have the same effect as springs be- 

 tween all the bones, so that no unyield- 

 ing substance can come in contact. 



On the same principle, a similar mode 

 of construction must be of great advantage 

 for wooden legs. We think wooden legs 

 of this sort have been already made by 

 another person, but if we are mistaken, 

 suppose Mr. Prisley will find it profitable 

 to have them made for sale. 



The joint in the middle of the crutch 

 seems a needless addition to the expense, 

 as the}^ can so very seldom require to be 

 divided. Perhaps for seibling to persons 

 in the country, it might be found more 

 convenient to forward the heads and 

 tubes, containing the springs by them- 



