1820.] Royal Academy of Sciences. 303 



proposes for laying down the strands have, it is true, no novelty 

 in a mechanical point of view; but this does not render them less 

 useful in respect to the making of ropes. The conclusion drawn 

 from the report is, that the perseverance exhibited by M. Duboul 

 in endeavouring to improve his manufacture, and the expense 

 he is at for that purpose, merit the highest praise ; that his two 

 machines, costing but little, may, in many cases, be of use in the 

 rope yards ; and the different degrees of twist proposed by M. 

 Duboul offer sufficient advantage in theory to merit trial and 

 examination with all the care and zeal that mechanics, who are 

 friends to the progress of the arts, can bestow upon them. 



Lamp of Messrs. Gagiieau and Brunet. — Committee, Messrs. 

 Gay-Lussac, Thenard, and Charlee, Secretary. 



The use of lamps with a double current of air is become so 

 universal, that it forms in itself a very considerable branch of 

 manufacture, which is continually increasing. New forms and 

 new compositions are invented every day. Amongst these 

 various kinds of lamps, many of v/hich answer their purpose very 

 well, there is one in particular that has for 20 years past con- 

 stantly remained superior to the rest, both with regard to the 

 briUiancy of its light and the regularity of its action ; namely, 

 Carcel's. But however perfect this lamp maybe, the expense of 

 its workinanship, the dehcacy of its construction, and the still 

 greater ditKculty of repairing it, rendered it desirable that intel- 

 ligent artists should modify this lamp in such a way as, while it 

 preserved all its advantages, its mechanism might be simplified, 

 and its execution, and especially its repair, be i'acilitated. Such is 

 the lamp of Messrs. Gagneau and Brunet. Upon a comparative 

 trial with one of the best of Carcel's for three successive nights, it 

 preserved its equality during 1 hours. The new lamp will even burn 

 12 hours ; but this length of time, to which the spnng will extend, 

 is nearly superfluous, as, at the end of 10 hours, the wick is 

 burned to a coal. The duraticm of the wick depends in some 

 measure on the more or less capillary quality of the cotton of 

 v/hich it is formed ; but that duration depends still more on the 

 goodness of the oil; in the experiments which were made, the 

 best oil was always employed. In an inverted application 

 which they have made of the pump, known for these hundred 

 years past by the name of le pompe des pretres, the authors 

 nave succeeded in substituting tv/o diaphragms of oiled silk for 

 Carcel's pump, and the friction being reduced nearly to nothing, 

 i tallowed of their omittina; two wheels, of lessenina; the force of 

 the movmg spring, and nevertheless of raising the oil to a greater 

 height. 'Ihe introduction of a reservoir of air renders this eleva- 

 tion constant and uniform; but in Carcel's lamp it is intermitting, 

 like the strokes of 'a piston. The power of giving to the bottom 

 of the lamp and the column a more hght and slender form is also 

 a very agreeable improvement. Another advantage is, the ease 

 with which it may be repaired, whenever the diapliragms requira 



