Scientific Intelligence. '-^Natural Philosophy j 183 



bolic reflector still appeared to be the most eligible means of con- 

 centrating the light. With the view of obtaining a powerful light, 

 Lieutenant Drummond first tried various pyrotechnical prepara- 

 tions, and afterwards the combustion of phosphorus in oxygen 

 gas ; but he found, in all these, that the light was ill defined, 

 and otherwise unsuited to the object in view. He then had re- 

 course to the light emitted by some of the earths and metallic ox- 

 ides, when ignited 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 effecting the comparison by the method of 

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

 this treatment, to be equal to 37 ; that emitted by zircon, 31 ; 

 and that by magnesia, 16. The best kind of lime for the 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 con- 

 trivance in geodesical operations. This lime, when the experi- 

 ment is most successful, emits a light exceeding 83 times that of 

 the brightest part of the flame of an argand lamp. In the fo- 

 cus of the parabolic reflector, at the distance of 40 feet, it is al- 

 most 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 officers to complete the connection of distant stations with 

 celerity, and in the most satisfactory manner. Various applica- 

 tions of it are contemplated ; among others, the connection of 

 the meridian of the Edinburgh Observatory with that of Dub- 

 lin, taking Benlomond as an intermediate station. 



METEOROLOGY. 



2. Deception occasioned by Fog. — " When at San Bias, a port 

 at the entrance of the Gulf of California, in January 1824, I 

 had occasion, in company with several of the officers of the ship 

 in which I then served, to visit the town of Sepic, situated about 

 fifty miles inland. The first eighteen or twenty miles of our 

 journey was over a low, swampy, flat, covered thickly with trees, 

 so as to obstruct the view in every direction. Afterwards, we. 

 began to ascend the mountainous tract that terminates the low 



