iSyi.] Engineering. 141 



for the. purpose of generating steam. The inventor, in communicating the 

 subject to a weekly contemporary, states as follows : — " The several experiments 

 that have been made show that the mechanism adopted for concentrating the 

 sun's radiant heat abstracts, on an average, during nine hours a day, for all 

 latitudes between the equator and 45 , fully 3-5 units of heat per minute for 

 each square foot of area presented perpendicularly to the sun's rays. A unit 

 of heat being equivalent to 772 foot-pounds, it will be perceived that, 

 theoretically, a dynamic energy of 2702 foot-pounds is transmitted by the 

 radiant heat per minute for each square foot ; hence 270,200 foot-pounds for an 

 area of 10 feet square. If we divide this sum by the adopted standard of 

 33,000, we ascertain that 100 square feet of surface, exposed to the solar rays, 

 develope continuously 8*2 horse-power during nine hours a day, within the lati- 

 tude before mentioned." Hence, he argues, " that those regions of the earth 

 which suffer from an excess of solar heat will ultimately derive benefits 

 resulting from an unlimited command of motive power, which will, to a great 

 extent, compensate for evils hitherto supposed not to be counterbalanced by 

 any good." The solar engine is composed of three distinct parts : — The engine, 

 the steam generator, and the mechanism by means of which the feeble 

 intensity of the sun's rays is augmented to such a degree that the resulting 

 temperature will exceed that of the lowest pressure of steam admissible in an 

 efficient engine. The motor itself is essentially a modern steam-engine, 

 utilising, to the fullest extent, the mechanical energy of the steam generated by 

 the concentrated solar rays. Mr. Ericsson withholds from the public, at present, 

 any description of his steam generator and concentration apparatus, and until 

 he shall have brought them to a more perfect state. 



Railway Gauges. — A most important question has lately been engaging the 

 attention of the Government of India, both in this country and subsequently in 

 India, namely, as to the gauge to be adopted for the railways of the future. 

 The existing standard gauge in India is 5 feet 6 inches ; but it was considered 

 that with a narrower gauge the requirements of the country might equally well 

 be met, and at a less cost per mile. The subject was accordingly referred to a 

 committee, consisting of Colonels Dickens and Strachey, and Messrs. Fowler 

 and Rendel. The result of their inquiries has been the submission of two reports, 

 the one by Mr. Fowler, wherein a 3 feet 6 inches gauge is recommended, and the 

 other by the remaining members of the Committee,- who advocate a gauge of 

 only 2 feet 9 inches. The general opinion of the profession appears to be in favour 

 of the wider gauge, some leading members being even averse to any deviation 

 from the existing standard gauge. The final decision rests with the Governor- 

 General in India, and that decision has not yet come home. 



Plain Cylindrical Boilers. — At the recent meeting of the Iron and Steel 

 Institute in South Wales, Mr. Jeremiah Head, of Middlesborough, read a 

 paDer " On the Efficiency and Durability of Plain Cylindrical Boilers." Mr. 

 Head, after giving certain statistics relative to these boilers, remarks that 

 their simplicity of construction is greater than in any other class of boilers, and 

 that in them an ordinary quality of plate and ordinary workmanship are alone 

 necessary. The diameter being moderate a high pressure may safely be main- 

 tained without the use of thick plates, and without the expense of double rivetting 

 and drilled holes, and that the risk of overheating for lack of water is much 

 less than with internally-fired boilers. The cost of such boilers varies with 

 the locality, but taking the rates at present ruling in the Cleveland district, 

 plain cylindrical boilers, with fittings, all of best material and workmanship, 

 cost ;£i8 10s. per ton delivered. Comparing these with internally-fired boilers, 

 Mr. Head shows that the cost of the latter is three times that of plain cylin- 

 drical boilers, whilst their saving in fuel amounts only to about g per cent. The 

 objection to these boilers — in common with all others externally fired — is that 

 they undergo a succession of expansions and contractions, and ultimately break 

 their backs, generally through a line of rivets. This drawback, however, it is 

 proposed to remedy by hanging them to rods and nuts, the latter resting upon 

 volute springs instead of upon rigid bearers, by which means they are enabled 

 to adjust themselves to each change of form of the boiler without materially 

 increasing or relaxing their hold. 



