1830.J [ 265 ] 



THE PROGRESS OF PHYSICAL DISCOVERY PART II. 



( Concluded from page 28.) 



IN 1818, chemistry was enriched by two entirely new substances, 

 brought to light by two Swedish chemists. The former was found by 

 Arfvedson, in a stone called petallite : it is both metallic and alkaline 

 that is, its oxyde is a fixed alkali, and it has received the name of lithion. 

 The latter was discovered by the celebrated Berzelius, in a manufactory 

 of sulphuric acid at Falun ; it is both metallic and acidifiable, of a grey 

 colour, yielding a red powder by trituration, and more analogous to sul- 

 phur than any other mineral. It bears the name of selenium, and has 

 hitherto been perceived in so extremely small quantities, that it seems 

 natural to believe that further researches may probably deprive it of its 

 rank as an elementary substance. Vauquelin's examination of Prussian 

 blue in this year is highly memorable, having led, among other results, to 

 the discovery of an acid, called cyanic acid. The experiments of MM. 

 Chevillot and Edouard upon that singular combination of oxyde of man- 

 ganese and potash called, from its facility in assuming different colours, 

 mineral cameleon led them to conclude that the intervention of oxygen 

 in the formation of cameleon tends to oxydise the manganese, and con- 

 vert it into a real acid ; so that cameleon is a manganesiate of potash ; 

 red cameleon being a manganesiate perfectly neuter, and green a manga- 

 nesiate with an excess of alkali. Another acid was detected also, in this 

 year, called pyromucic, by M. Hontou-Labillardiere. in the saline matter 

 produced by the sublimation of the mucic acid yielded by sugar of milk, 

 and which appears to have been confounded by Tromsdorf with succinic 

 acid. Fertile as this period had already been in acids, there was yet 

 another ascertained by M. Chevreul, in the continuation of his researches 

 into soap and fat, w T hich was distinguished by the name of the delphinic. 



The science of meteorology, from the irregularity of the atmospheric 

 phenomena, especially in our climate, is yet very far distant from the 

 rank of a positive science. Every additional observation, however, 

 increases its importance ; and we are especially indebted to that indefa- 

 tigable and enlightened naturalist, the Baron Humboldt, for his remarks 

 made this year in the torrid zone, in whose climate the atmospheric phe- 

 nomena are the most simple and regular. Baron Humboldt directed his 

 attention to the connexion between the declination of the sun and the 

 commencement of the rains in the north part of the torrid zone. As soon 

 as the sun approaches within one league of the tropic, the breezes from 

 the north are replaced by calms, or winds from the S.E. ; the transpar- 

 ency of the air diminishes ; the unequal refraction of its settings makes 

 the stars shine at 20 degrees below the horizon ; the vapours gather 

 together in clouds, and thunder is frequently heard. These phenomena 

 he explains by the inequality which exists between this part of the 

 torrid zone and the adjoining temperate zone. When the sun is to the 

 south of the equator, it is the winter of the northern hemisphere ; and 

 the air of the temperate zone is as different as possible from that of the 

 torrid. It flows constantly into the former in a fresh breeze, which car- 

 ries the hot and damp air into the height of the atmosphere, whence it 

 returns, re-establishing the equilibrium, and bringing with it moisture: 

 the average heat also is less by five or six degrees in the time of drought 

 than in the time of rain ; but the south-east winds do not act like those 

 of the north, because they come from a hemisphere abounding more 



M.M. New Series. VOL. IX. No. 51. 2 M 



