1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



36S 



Let us now consider thf case of flexure, and let us suppose the 

 ratio of the length to the smallest dimension of the cross section to be 

 so great, that flexure may commence before a permanent alteration 

 has taken place. In this case the strain due to Iheefftct u/fe.viire alone, 

 increases as the versed sine ; and M. Lamarle shows that an almost 

 imperceptible increase of the pressure corresponding to tlie initial 

 flexure, is sufficient to cause an instant alteration of the el.isticity. 

 Hence the second principle of the author, not absolute, but suthclently 

 general to include all the cases which might escape the first, under the 

 circumstances usual in practical applications. 



Theso two principles taken together, ofTer a satisfactory solution to 

 the question of beams loaded vertically. — Ibid. 



ECONOMY OF JACKETS FOR STEAM ENGINES. 



Note -upon the Injltience of Jockets upon Steam Engines. 



Combes. 



By M. 



A steam engine built by Farcot, was provided with an envelope to 

 the cylinder, into which the steam was freely admitted from the 

 l)oiler, and from which it passed as required into the cylinder. It 

 having become necessary to repair this jacket, it was found that the 

 expenditure of fuel was increased in the ratio of I'l to 10. A similar 

 fact has also been observed in an engine of the same builder, erected 

 near Sedan. A series of experiments was instituted by M. Combes, 

 and conducted as follows : — 



First, the machine was worked as usual, the steam being admitted 

 to the jacket, and from the jacket to the cylinder : these experiments 

 were continued for four days, the quantity of water pumped into the 

 boiler being accurately me^isured, and the quantity of coal weighed ; 

 the amount of water condensed in the jacket was also ascertained, and 

 every half hour the tension of the steam in the cylinder was measured 

 by an indicator, and at the same time the pressure in the boiler, and in 

 the condenser, were taken by gauges, and the number of strokes per 

 minute of the piston counted. 



Second, for three days the machine was worked by conducting the 

 steam directly into the cylinder from the boiler, the jacket containing 

 air only. The same observations as before were carefully made. 



Third, for three days the steam was conducted directly to the cylin- 

 der, but the jacket was kept in communication willi the boiler, and 

 was, consequently, filled with steam. The same observations were 

 made as before. 



The following are the results of the table : — 



M. Combes attributes the increased quantity of fuel necessary when 

 the jacket is not used, to the formation of water by condensation of 

 the steam during its admission into the cylinder, and the consequent 

 necessity of furnishing more steam to supply this loss by an additional 

 evaporation from the boiler. — Ibid 



OXIDE OF ANTIMONY A SUHSTITUXE FOR WHITE LEAD. 



M. de Uuolz, in the Compter Rendzis, states that the oxide of anti- 

 mony, (flowers of antimony,) possesses the following advantages over 

 white lead : — by means of a manufacture selected by us, it is obtained 

 directly from the native sulphuret of antimony — Its adoption will give 

 a new vigour to the languid working of the mines of antimony which 

 abound in France. — Its price of production is less than the third of 

 that of white lead of average quality. — It may be immediately ground 

 with, or without, other manipulation. — The workmen who are engaged 

 in its manufacture, will be exempt from all danger, — and it is altoge- 

 ther improbable that the painters who may employ it mixed with oil, 

 will experience the least inconvenience /rom it. 



THE CONSTRUCTION OF CHIMNEYS. 



[We have been requested to give publicity to the following trans- 

 lation of a notice issued pursuant to a resolution passed on the 18th 

 May, 1813, by the Lower Austrian Society of Manufactures.] 



Notice. 



A prize to be given by the " Society for the encouragement of Arts 

 and Manufactures " of Vienna, in Lower Austria, for the best treatise 

 on " the most advantageous dimensions and arrangements of chimneys, 

 and other essential parts of furnaces used in manufactories and similar 

 places. 



Notwithstanding the many investigations that have been made, 

 there still exists a great deficiency in our pvrotechnical knowledge as 

 to the dimensions of several most essential parts of furnaces, parti- 

 cularly those of chimneys, which are at present determined upon, on 

 very uncertain definitions. It is known by experience how very much 

 the situation of a chimney operates upon the success of an industrious 

 enterprize, and how detrimental some arrangements partly in the ex- 

 pense of construction, and partly in the consumption of fuel. 



Chimneys varying in height are used to furnaces for boilers to 

 steam engines of equal power, without any difference of result in the 

 consumption of fuel, whereas it has been found that low and narrow 

 chimneys aftbrd the greatest ads-antages in the economy of fuel. 



Whether is it more desirable, therefore, with a large furnace to 

 have several narrow chimneys or one of large diameter ? What ex- 

 tent of draugiit is requisite? What influences chimneys have on the 

 furnaces by attenuating the air? are questions which experience has 

 not yet elucidated. 



In order to combine principles which are based upon fixed laws, 

 examine the causes, and frame a theory, which from observation will 

 hold good in practice, so that means may be afforded in erecting fur- 

 naces to determine a priori the right dimensions for the chimneys and 

 flues of large furnaces, the "Society for the encouragement of Arts 

 and Manufactures," resolved at a general meeting on the 8th May, 

 1843, (similar to the example set by the Societe industrielle in Mick- 

 Ihausen) to offer a reward of a small gold medal to the author of the 

 best treatise, in accordance with the aforesaid proposals. The medal 

 is to be adjudged at the general meeting in May 1845. The treatises 

 are to be delivered before the 1st of February 1845, by persons domi- 

 ciled in Vienna, to the Secretary of the Society, who will give the re- 

 quisite receipts for the same. 



Treatises published before the expiration of 1813, will be admitted 

 to the competition. Such treatises to be accompanied by a sealed 

 note, containing both the name of the author and address, also a 

 similar motto or sign to the one written on the title-page of the trea- 

 tise. 



The successful treatise, and that nearest to it in merit, will be 

 opened at the general meeting for adjudging the prize. The candi- 

 dates for the prize retain their right of publication up to the end of 

 1S45, after which the right devolves to the societv in case the author 

 has not published his work. The unsuccessful treatises will be re- 

 turned at the Society's office to authorized persons, on giving up the 

 Secretary's receipt. 



THE NUNHEAD CEMETERY AFFAIR. 



Sir — The information given in your last number, relative to the 

 course pursued in the competition for the two chapels at the Nunhead 

 Cemetery was altogether new to me, for I had not even so much as 

 heard of there having been any exhibition of drawings, — which last, 

 indeed, appears to nave been rather more for form's sake than any 

 thing else, if it really consisted of " more than four hundred drawings," 

 yet was kept open only two days ! — hardly time enough for persons 

 to learn that there was any exhibition of the kind at all, it not having 

 been previously amiounced by public advertisement. That this ex- 

 hibition was little more than a nominal one — at least quite a private 

 one — is tolerably evident from the fact of its being kept so close a 

 secret, that not even any mention of it transpired through any of those 

 journals and periodicals which attend to all matters connected with 

 art, and which, had they been aware of it, would hardly have failed to 

 speak of what is by no means a common occurrence. At all events 1 

 may confidently say that no card was sent to the "Civil Engineer," 

 apprising you of the exhibition and soliciting your inspection of the 

 designs, otherwise we should have had some remarks upon them at 

 the time. As far therefore as that point is concerned, I must beg 

 leave to differ from the opinion, expressed in your Journal, since I do 



