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THE POPULAR SCIENCE MONTHLY. 



glowing impression of the exact size and 

 shape of the hollow flame. The moment 

 the gas is extinguished, or the flame re- 

 moved to the slightest distance from the 

 solid, the effect ceases. This appearance, 

 and the blue tinge which is said to be pecul- 

 iar to the hydrogen-flame, are really due, 

 according to Mr. Barrett, to the presence 

 of sulphur, and so delicate is the reaction 

 with this substance, that, without the great- 

 est care in purifying the gas, and cleansing 

 the surfaces with which, when burning, it is 

 brought in contact, sufficient sulphur will 

 be present to perceptibly color the flame. 

 The least trace of phosphorus is also made 

 apparent by the hydrogen-flame, by the 

 production of a vivid-green light. When 

 made to play upon the surface of clean tin, 

 or some alloy of tin, a fine scarlet color is 

 almost instantly produced, though the ap- 

 pearance is less vivid than with either sul- 

 phur or phosphorus. 



Many gases also impart color to the hy- 

 drogen-flame ; hydrochloric-acid gas giving 

 a reddish-brown flame ; ammonia gas a yel- 

 low flame, etc. Carbonic-acid gas, even in 

 the smallest proportions, gives the flame a 

 pale lilac tinge, the color being most marked 

 at the base of the flame. 



Mr. Barrett suggests that the delicacy 

 of these various reactions makes it possible 

 to turn them to valuable practical account, 

 in the detection of the substances named. 

 When, for example, the air of a room has 

 become vitiated by the accumulation of an 

 undue amount of carbonic acid gas, the 

 hydrogen - flame, by means of suitable ap- 

 paratus, will readily make the condition 

 known. This practical side of the subject 

 is now engaging Mr. Barrett's attention. 



Recent Cave Explorations. Some highly- 

 important discoveries have lately been made 

 in a cave near Luchon, France, by M. Piette, 

 of the Geological Society. The soil of the 

 casern consists of several layers the lower- 

 most ones being characterized by the bones 

 of the reindeer, and by dressed flints like 

 those of the grotto of Laugerie-basse. 

 These layers enclose, in addition to human 

 bones, a large fauna, and particularly a 

 considerable quantity of carved bones and 

 stones. Nowhere else has so great an ac- 

 cumulation of prehistoric works of art been 



found. The figures often cannot be recog- 

 nized ; still on the bones are seen some 

 designs of considerable finish. M. Piette 

 mentions, among other carvings, some that 

 represent flocks of wild-goats, and herds of 

 reindeer, the head of a rhinoceros, a wolf, 

 horses, a lion's head with mane, etc. These 

 valuable remains are buried in a black soil, 

 filled with ashes. Near the surface of this 

 layer the fauna is the same as it is below, 

 but the carvings are very different from 

 those underneath, and show a very marked 

 decadence. While the lower ones reproduce 

 Nature exactly, with extreme care and a cer- 

 tain minuteness of observation, the upper 

 ones are fantastical and not after Nature, aa 

 well as ruder than the others. All the hu- 

 man bones, especially the bones of the skull, 

 are reduced to small fragments, and all have 

 notches and incisions more or less deep. 

 This, M. Piette takes as an evidence of can- 

 nibalism. The topmost layer is hard and 

 compact. 



Relation of Death-rate to Temperature. 



In a little work on the climate of Uck- 

 field (England), Mr. J. Leeson Prince has the 

 following concerning the influence of tem- 

 perature on the death-rate : 



" The mean annual temperature varies 

 5.3, viz. : from 51.93 in 1857, to 46.62 in 

 1845, and although at first sight this differ- 

 ence may not appear considerable, yet it is 

 sufficient to exert an enormous influence 

 upon the general character of the seasons, 

 the produce of the soil, and the health of 

 the population. The registrar - general's 

 interesting returns have fully established 

 the important fact that there is a very in- 

 timate connection between temperature and 

 mortality. Whenever the mean tempera- 

 ture falls to 45 or thereabouts, the number 

 of deaths from diseases of the respiratory 

 organs increases ; and, should it fall below 

 40, the death-rate from such diseases is still 

 higher. When a period of intense cold pre- 

 vails, so that the temperature scarcely rises 

 above the freezing-point for two or three 

 weeks, the number of deaths will be found 

 to exceed what takes place during an epi- 

 demic of cholera or scarlet fever. But, 

 when the mean temperature rises to 55, 

 there will be an increase in the number of 

 deaths from diseases of the abdominal via- 



