933 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



must then be wrapped in blotting paper and carefully laid under 

 warm sand, or upon chalk or gypsum. When dry, the potatoes 

 will be found to have shrunk to about one-half their original vol- 

 ume, and in external appearance they will exactly resemble meer- 

 schaum. By treating the macerated potatoes with caustic soda, 

 the starch and cellular tissues are made to unite and form a sub- 

 stance resembling horn. Turnips may also be similarly treated, 

 so as to resemble stag's horns. Thin slices may be used as veneers 

 and soaked in glycerine and Avater they become flexible as leather. 

 Carrots thus treated reseml)le coral, and may be used for handles 

 of knives, umbrellas and whips. 



Pins and Eyes. 

 The London Engineering, in an article upon this subject, says 

 that in all cases, but more particularly in bridge work, it is 

 important that the size of the pins and eyes should be so propor- 

 tioned to the strain upon them that they will be of equal strength 

 witli the parts which they connect. In machiner}-, when the parts 

 are subjected to motion, sufficient bearing surface has to be pro- 

 vided to prevent heating, and it is generally this consideration 

 which governs the size of the parts, those proportions which give 

 the requisite bearing surface l)eing generally ampl}"" sufficient as 

 far as mere strength goes. After giving the results of experiments 

 tried to determine the proper proportions of the eyes of the links 

 and the connecting j^ins of the iron suspension bridge over the 

 river Dnieper at Kiefl", the chains of which weighed over 1,600 

 tons, and stating the proportions recommended by Sir Charles Fox 

 and Professor Kankine the Engineering expresses the opinion that 

 when circumstances will allow its being done, the best way to 

 obtain the requisite bearing surface for the pins of connecting 

 links of small thickness in proportion to their section, is to increase 

 the thickness of the eyes beyond that of the links themselves. 

 This allows the metal around the eye to be made narrower, and it 

 thus consequently diminishes the inequality of the strain through- 

 out its section. Where the links are to be connected by a square 

 section, or are of considerable thickness in proportion to their 

 area, this thickening of the eye becomes unnecessary, as sufficient 

 bearins; surface is cfiven without it. A rule for the size of eves, 

 which has been much used, and which gives generally good results. 

 is to make the outside diameter of the eye equal to twice the 

 diameter of the pin pas«cd through it, and then to increase the 

 thickness until the requisite section area is obtained. 



