\QQ . PALPABLE MATHEMATICS. 



INK IN RELIEF. 



Pefideratum ; a It would be a very ufeful invention, if an ink could be 

 \'jj b,e . and tan- formed which in coming from the pen fhouid leave a mark 

 that would project. This ink would have the double advan- 

 tage of enabling the blind and thofe who fee to read at the 

 fame time writing, the figures of arithmetic, the characters of 

 algebra, and the notes of mufic. I have not yet thought of 

 any fatisfa&ory expedient for this purpofe, and fhall not 

 therefore enter into any further detail. 



GEOMETRY. 



Saundeifoivs Saunderfbn, in order to coriftruct geometrial figures, placed 



method of torm- pj ns ; n holes made in a board, and palled threads from one pin 



ing geometrical r , » r i 



figures with pins to another. My method appears to be preferable in every re- 



and threads. fp e ft . ft [ s tn i s . w i tn four fides of wood I have conftru6ted a 



thod; by wires frame, the length of which is about 20 inches, the breadth 16> 



•naflatcuihion. an d thicknefs three quarters of an inch. I have covered the 



two faces with woollen cloth rather open and foft, and have filled 



the intermediate fpace with other loofe and foft woollen cloth, 



fo as to form a flat cufliion three quarters of an inch thick. 



I' have very fmall iron wires, bended at right angles at the 



two ends, which are pointed and polifhed. Thefe iron wires 



areeafily fixed in the cufliion, and form lines in relief, which 



nothing can derange. I have'an aflbrtment of all lengths, as 



well as circles, femi-circles, parabolas, ellipfes, &c. Laftly, 



I have letters in relief, with a point in order to fix them on the 



cufliion. 



This method is % means of this little apparatus, there is no figure in geo- 



>ery ready and m etry, however complicated, but may very fpeedily be re- 



comprehenfive. prefented {n ^jfcfc 



. We might likewife, and with advantage, ufe this cufliion 

 for making figures with pins and threads ; but this method, 

 though better than that of Saunderfon, is not fo good as the 

 iron wires here defcribed. Experience is decifive in this re- 

 fpea. 

 and is applicable At is ea fy to perceive that the above method is likewife the 

 to mufic, &c. belt for the notes of mufic ; but the limits I have adopted will 

 not allow me to enter into further details. 



XL Obfervations 



