114 REPORT — 1851. - 



T he use of gussets is earnestly recommended as being infinitely superior to and 

 more certain in their action than stay- rods. They should be placed in lines diver- 

 ging from the centre of the boiler, and made as long as the position of the flues and 

 other circumstances in the construction will admit. They are of great value in re- 

 taining the ends in shape, and may safely be relied on as imparting an equality of 

 strength to every part of the structure. 



On Railway Chairs and Compressed Wood Fastenings. 

 By Charles May, F.R.A.S. 



The author brought these observations forward with a view to giving information 

 to such persons as might incline to visit the manufactory of them at the Orwell 

 Works, which would be open to any visitors to the British Association. 



The chairs were those used upon narrow gauge lines with cross sleepers, and the 

 mode of casting effected great accuracy, so that each was practically a counterpart 

 of the rest ; and so extensively had this system been adopted, that more than fifty 

 railways had been supplied with them. 



The fastenings are those pieces of wood called treenails and wedges ; the former 

 being used as nails to fasten the chairs to the sleepers, sind the latter to secure the 

 rails in the chairs. 



Mr. May described the structure of wood as a bundle of tubes of irregular shape, 

 which, when emptied of the sap by drying, might be squeezed together into a smaller 

 bulk, just as a bundle of leaden pipe might be compressed ; but in the case of wood, 

 which is elastic, it is found necessary to keep the compressing power on it for some 

 time, or it would more or less re-expand ; if, however, during the continuance of the 

 compressing force, a small degree of heat is applied, the wood takes a " set," which 

 is permanent as long as the article is kept dry ; but the power of capillar)' attraction 

 not being destroyed by the process, the fastenings, when used upon the railways, 

 expanded like a cork driven into a bottle, and this kind of elastic fastening was found 

 to produce not only increased security as compared with other modes of fastening, 

 but also a smoother motion in the carriages. 



The same mode of compression is adopted for the treenails of ships, and from a 

 series of experiments made by a Committee appointed by the Admiralty, it appeared 

 that these compressed treenails had 29 per cent, more transverse and 60 per cent, 

 more adhesive strength than those in ordinary use ; yet even these advantages had 

 not secured their adoption. 



On the Application of Chilled Cast Iron to the Pivots of Astronomical In- 

 struments. By Charles May, F.R.A.S. 



In laying before this Section a few observations on this subject, some preliminary 

 remarks on the process of chill casting and its previous application to other purposes 

 seem to be requisite. 



" It has long been known that if a mould for casting iron be made of iron, or 

 partly of iron and partly of sand, that portion of the casting which has run against 

 the iron becomes what is technically termed ' chilled,' and is indicated by a white 

 crystalline structure to a depth depending upon various conditions of temperature 

 of the mould and the metal run into it, as well as of the chemical composition of the 

 iron. The practical utility of chill casting depends on the fact, that the part thus 

 rendered crystalline is of extreme hardness, nearly equal to that of hardened steel ; 

 whilst the remainder of the casting may be as soft as iron cast in the ordinary sand- 

 moulds. 



" The rationale of the effect thus produced is not well understood ; cast iron is a 

 compound of iron with variable proportions of carbon, and these proportions have 

 not, as I believe, been j'et reduced to anything like atomic order : some statements 

 give as much as 15 per cent, of carbon in verj' soft pig iron, and such iron exhibits 

 very little or no tendency to chilling. Practical experience is at present the only 

 guide to the production of the desired effect ; in some cases a very thin hard stratum 

 is desired, in others a considerable depth ; and this stratum may be varied from an 

 almost imperceptible white line to half or three-quarters of an inch in depth, this latter 



