Magnetism — Meteorology — Chemistry. 181 



11. On the Powerful Effect of Burning-Glasses at great Heights. — The 

 extreme transparency of the air on high mountains, which hinders the ca- 

 lorific rays which traverse it from heating it directly, gives rise to several 

 effects different from those we observe on the surface of the earth. The 

 heat of the ground, for example, which absorbs the solar rays on those sum- 

 mits, is often, as M. Ramond observes, out of all proportion to that of the 

 atmosphere. When these rays, therefore, are collected in the focus of a 

 lens, they have much greater power than when they traverse a thick and 

 less transparent atmosphere. He found that a lens of a very small diame- 

 ter was sufficient to set fire to bodies, which a lens of double the diameter 

 would scarcely heat in lower regions. M. Ramond supposes that the tem- 

 perature of the different colours of the spectrum might be well ascertained 

 on lofty summits. 



The Memoir of M. Ramond, which contains these two notices, is entit- 

 led, on the Meteorology of the Pic du Midi, and was read at the Academy 

 of Sciences, on the 13th March 1826. — Le Globe, March 16, 1826. 



MAGNETISM. 



12. Diurnal Variation of the Needle in the Arctic Regions. — From a pa- 

 per by Captain Parry and Lieutenant Forster, read before the Royal So- 

 ciety on the 13th April last, it appears that the diurnal variation of the 

 needle at Port Bowen sometimes amounts to 7° or 8°, and is never less than 

 1°. These able observers are said to have discovered a decided connection 

 between the diurnal variation, and the positions of the sun and moon. 



METEOROLOGY. 



13. Meteorological Observations on the 17th of July next. — Printed sche- 

 dules have been circulated by the Royal Society of Edinburgh, with a re- 

 quest that observations on the thermometer, barometer, rain-gage, &c. and 

 general state of the weather, should be made in various parts of the king- 

 dom on the 17th of July next, and at every hour of that day, from one 

 o'clock in the morning to twelve o'clock at night. It is much to be wish- 

 ed that corresponding observations should be made in England and Ire- 

 land, and on the Continent of Europe on the same day, as very important 

 results may be deduced from such a series of simultaneous observations. 

 Schedules and directions for making the observations, may be obtaiued, by 

 applying to Messrs Taits, booksellers, Prince's Street, Edinburgh. 



II. CHEMTSTKY. 



1 !. Dr Henry's Analysis of a Crystalline Compound of Hyponiirous and 

 Sulphuric Acids. — This substance was formed in the process for making 

 sulphuric acid in leaden chambers, and its production appears to have been 

 determined by intense cold. The product of sulphuric acid having unac- 

 countably fallen off, it was suspected that the ventilating pipe was closed 

 with sublimed sulphur ; but, when examined internally, it was found to 

 have been completely stopped by a crystalline solid, not unlike borax in 

 appearance. When kept for a day or two in a warm room, it assumed a 

 soft pasty form ; and, by standing still longer, a liquid of rather thick con- 



