Bnrning Gas for the purpose of Illumination. 301 



go out. In all othffj!' respects, globes have undeniable advan- 

 tages ovei' fi'amed lanterns, as they protect the flames better 

 in high winds, and they are kept up at much less expense. 



Some years ago I pointed out to the Commissioners of Po- 

 lice of this city, that advantage might be taken of the acknow- 

 ledged good properties of the globes for lighting the streets, 

 and the alleged defect be obviated by constructing the tin tops 

 with chimneys which should reach down to the points of the 

 flames, and by their current carry off the water while still in 

 a state of vapour, and so prevent it from being condensed on 

 the sides of the globes. This plan was immediately tried, 

 and having been found successful, was adopted in all the 

 lamps erected subsequently. It occasionally happens, that 

 from the jet being deranged, the gas is directed past the tin- 

 chimney instead of into it, and if the weather be cold, it is 

 immediately observed that a deposition of water takes place 

 inside the globe, and its sides become dim. The adjustment 

 of the bm'ner restores the proper action, and the globe re- 

 mains bright. This plan having now stood the test of many 

 years' experience may safely be recommended for adoption 

 wherever new street lamps are erected. 



Abridgment of an Essay on the Construction of Oblique Arches. 

 By Edward Sang, M.S. A,, Civil Engineer, Edinburgh. 

 Communicated by the Society of Useful Arts for Scotland.* 



Scarcely any branch of civil engineering bears so closely 

 on the advancement of civilization as the art of road-making. 

 The immense simis that are annually expended on them evince 

 the importance of our roads. Our object is not merely to find 

 a path from one town to another, we must be transported in 

 the most expeditious manner possible. Is there a declivity ? 

 thousands are spent to remove it : Is a road suspected of 

 being a few yards longer than is needed ? a new line is imme- 



* Rotul hefori; tlio Socioty for tlio Ent-ourngeincnt of tlio Useful Arts in 

 Scotland, on llJtli Novcrnbor and 2d Doceiiiber 1835; 27th Januaiy 1836, 

 and IGth May 1838. 



VOL. XXVIII, NO. LVI.— APRIL 1840. X 



