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THE POPULAR SCIENCE MONTHLY. 



ual impressions from sounds. When a cer- 

 tain note is struck upon the piano, the 

 brothers at once have a sensation of a cer- 

 tain corresponding color, which is not, how- 

 ever, identical for both. Thus the note 

 which produces in the one the impression 

 of dark Prussian blue, produces in the other 

 that of dark yellow. They do not, however, 

 perceive all colors on occasion of hearing 

 sounds. One of the brothers has sensations 

 of yellow, brown, and violet, most frequent- 

 ly ; while blue, yellow, and brown, are most 

 frequent with the other. One of them never 

 has the sensations of red, green, black, or 

 white, awakened by musical notes, though 

 on one occasion he says that, suddenly hear- 

 ing a noise from the filing of a saw, he had 

 the sensation of green. No doubt it is very 

 difficult to be secure against deception in 

 such a matter as this ; but we may add that 

 Prof. Briihl, of Vienna, after thorough in- 

 vestigation, is satisfied that there is no 

 fraud. 



Meteorological Observations In the Tpper 

 Atmosphere. We take, from the Proceed- 

 ings of the French Academy of Sciences, the 

 following interesting account of meteorologi- 

 cal observations made by M. G. Tissandier 

 during a balloon-ascension in the month of 

 February last : Six gentlemen accompanied 

 M. Tissandier on his aerial voyage. The 

 balloon, whose capacity was 2,000 cubic 

 metres, was filled with illuminating gas. 

 The ascent was made from the city of Paris, 

 and the voyagers soon found themselves at 

 an altitude of 1,200 metres, and enveloped 

 in a dense layer of cloud. Having risen 

 above this stratum of cloud, they entered a 

 region where the sun's rays were intensely 

 bright, and the heavens of a deep blue. 

 For about three hours they sailed at an ele- 

 vation of about 400 metres above the 

 clouds. The shadow of the balloon, as it 

 fell on this ocean of vapor, was very re- 

 markable. At an elevation of 1,350 metres 

 the shadow of the balloon itself had no 

 halo, though one was risible around the 

 shadow of the boat. At 1,700 metres the 

 balloon's shadow was surrounded with 

 rings of rainbow hues. Again, and at the 

 same elevation, there appeared three dis- 

 tinct concentric halos. In all cases the 

 violet was on the inner and the red on the 



outer side of the halos, but the blue and 

 the orange colors were most clearly visible. 



The temperature was very high, being 

 17.5 Cent., and the sun's rays so hot as to 

 burn the face. The greatest altitude at- 

 tained was 2,000 metres. As the balloonists 

 descended through the cloud, a copper wire 

 suspended from the boat gave strong indi- 

 cations of electricity. On reaching 1,200 

 metres, where the cloud was densest, the 

 voyagers were unable to see the balloon 

 above them, and were chilled by the cold, 

 the thermometer showing 2 Cent. The 

 copper wire gave out vivid sparks, and was 

 quickly coated with ice-crystals, which glis- 

 tened like diamonds. Similar crystals formed 

 on the boat, and on the clothes and beards 

 of the voyagers. 



The descent was made at Montireau, 

 distant 120 kilometres from Paris. Time, 

 3 hours and 45 minutes. M. Tissandier 

 thinks that the dense opaline cloud through 

 which he passed is made up of ice-crystals. 

 The paper by Mohr, in The Popular Sci- 

 ence Monthly for May, shows that vapors 

 can resist crystallization at a far lower 

 temperature than 2 Cent. 



Social Relations of Ants. At the Con- 

 gress of Swiss Naturalists, which assembled 

 in August of last year at Friburg, Auguste 

 Forel read an address upon the " Social Re- 

 lations of Various Species of Ants." A 

 nest is sometimes occupied by a community 

 belonging to one species, sometimes by a 

 community made up of two or more species, 

 but all have the three classes of males, fe- 

 males, and workers. In a mixed commu- 

 nity there will sometimes be found slaves 

 that is, workers of a different species made 

 captive while still in the cocoon. When 

 these emerge from their silken envelope, 

 they become the friends and willing thralls 

 of their captors, as though such were their 

 natural destiny. A mixed community em- 

 braces all three sexes of the captor species, 

 but only workers, or neuters, of the cap- 

 tive. The Polyergus rufescens and the For- 

 mica sanguinea both make slaves of the 

 Formica fusca. The Polyergus is extremely 

 indolent, but the F. sanguinea assists his 

 slaves in their work. 



There are certain species of ants which 

 live by the labor of others without enslav- 





