453 Proceedings of PhilosopJdcal Societies. [June, 



in all these, that the light was ill-defined, and otherwise un- 

 suited to the object in view. He then had recourse to the 

 light emitted by some of the earths and metallic oxides, when 

 ionited by the flame of alcohol, urged by oxygen gas. Taking 

 the light of the brightest part of the flame of an Argand lamp 

 as unity, and eftecting the comparison by the method of sha- 

 dows, he found the light given out by quicklime, when under 

 this treatment, to be equal to 37 ; that emitted by zircon 3 1 ; 

 and that by magnesia 16: oxide of zinc was also tried, but it 

 quickly wasted away, and gave out less light even than mag- 

 nesia. The best kind of lime for the intended purpose is chalk- 

 lime, which admits of being turned readily into small balls, 

 having a stem, and to which the regularity and truth of surface 

 can be given, which are essential to the production of the well- 

 defined image, necessary for the perfect use of the contrivance 

 in geodesical operations. 



This lime, when the experiment is most successful, emits a 

 light exceeding 83 times that of the brightest part of the flame 

 of an Argand lamp. In the focus of the parabohc reflector, at 

 the distance of 40 feet, it is almost too dazzling to look at. 



From the perfect success which attended the employment of this 

 mode of illumination, on one occasion in Ireland, last year, it is 

 expected that it will enable the ofticers employed in the survey, to 

 complete with celerity, and in the most satisfactory manner, 

 the connection of distant stations. Lieut. Col. Colby pur- 

 poses to connect, by means of this invention, the meridian of 

 the observatory on the Calton Hill, at Edinburgh, with that of 

 Dublin, taking Ben Lomond as an intermediate station ; one 

 side of the triangle in which operation will measure above 90 

 miles. Other apphcations of it are also contemplated. 



Lieut. Drumniond found that a mixture of hydrogen and 

 chlorine gases, exposed to the light given out by the lime, was 

 converted into muriatic acid ; and that when the light was 

 decomposed by a prism, the violet ray it contained had a 

 marked eff'ect on chloride of silver. 



A note addressed to the author by Mr. Herschel was an- 

 nexed to this paper, stating the results of a cursory optical 

 examination of the light emitted by the incandescent lime. It 

 contains all the usual rays, and three of them remarkable in 

 quantity and quality : viz. a red, intermediate between the red 

 and orange of the solar spectrum, but nearer to the latter ; a 

 yellow ; and a green. Mr. Herschel points out as a curious 

 fact, that a red of the above character should be yielded by 

 lime itself, whilst the colour given to burning bodies by the 

 combinations of that earth is a brick-red, very distinct from 

 the hue imparted by strontian, which is of a carmine tint. 



May 11. — Sir J."S. Copley, His Majesty's Attorney-general, 

 and L. A. Dela Chaumette, Esq. v/ere admitted Fellows of the 

 Society : A paper was read, On the Production and Formation 



