ual impressions from sounds. When a certain note is struck upon the piano, the brothers at once have a sensation of a certain corresponding color, which is not, however, 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 frequently; 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 hearing 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. Brühl, of Vienna, after thorough investigation, is satisfied that there is no fraud.
Meteorological Observations In the Upper Atmosphere.—We take, from the Proceedings of the French Academy of Sciences, the following interesting account of meteorological observations made by M. G. Tissandier during a balloon-ascension in the month of February last: Six gentlemen accompanied M. Tissandier on his aërial 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 elevation of about 400 metres above the clouds. The shadow of the balloon, as it fell on this ocean of vapor, was very remarkable. 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 distinct 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 attained was 2,000 metres. As the balloonists descended through the cloud, a copper wire suspended from the boat gave strong indications 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 glistened 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 Science Monthly for May, shows that vapors can resist crystallization at a far lower temperature than 2° Cent.
Social Relations of Ants.—At the Congress of Swiss Naturalists, which assembled in August of last year at Friburg, Auguste Forel read an address upon the "Social Relations 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, females, and workers. In a mixed community 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 embraces all three sexes of the captor species, but only workers, or neuters, of the captive. The Polyergus rufescens and the Formica 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-
