FRAGMENTS OF SCIENCE. 



137 



the female Arabian camel; but when the 

 parentage is reversed the progeny is useless. 

 General Harlan is said to have marched two 

 thousand Bactrian camels four hundred miles 

 and crossed the Indian Caucasus in ice and 

 snow, with the loss of only one auimal, and 

 that by an accident. This camel is native to 

 the high plateaus, steppes, and deserts of 

 Mongolia and South Siberia, and it has been 

 found wild on the plain of Tsaidam, main- 

 taining itself in this "arid, cold, and wa- 

 terless region, where the herds are said to 

 travel seventy miles to drink. Nothing," 

 we are further told, " but too much comfort 

 or a damp climate seems to hurt it. For 

 food it prefers dry, salty plants and bushes 

 and grows sick and lean on good pasture. 

 The salty efflorescence of the steppes is ea- 

 gerly eaten by it, and in this country it pre- 

 fers dry food, especially wheat straw and 

 hay. Prjevalski's camels would eat almost 

 anything — straw, bleached bones, old pack 

 saddles, straps, and leather. The Mongols 

 told him of camels which had been without 

 food a long time, and then devoured an old 

 tent belonging to their owner. They even 

 ate meat and fish, and one of the traveler's 

 camels made a meal of the bird skins ready 

 for stuffing." 



Nicaragua and its Ferns. — Tropical Amer- 

 ica is described by B. Shimek, in a paper on 

 the Ferns of Nicaragua, as the fern paradise 

 of the earth. " No other corresponding di- 

 vision of the earth's surface," he says, " pre- 

 sents as great a total number of species, or 

 as many species which are peculiar to it. 

 Nowhere else is the great variation in form 

 and size, in structural characters and habits 

 of growth, and in the arrangement and char- 

 acter of the reproductive organs, better shown 

 than here. This richness in the fern flora, 

 exhibited in almost unlimited variety, is, no 

 doubt, accounted for by the topography and- 

 contour of that part of the American conti- 

 nent which lies within the tropics. It is nar- 

 row when compared with the continents of 

 the Old World, and it contains high moun- 

 tain chains, which form its longest axis. Its 

 narrow form brings all of it more or less 

 within the influence of the adjacent oceans, 

 which furnish to most of it an abundance of 

 moisture. Its high mountains supply all the 

 conditions effected by altitude, and, more- 



over, cut off the otherwise abundant moisture 

 from certain areas. We have thus within 

 comparatively restricted limits all the possi- 

 ble degrees of moisture and temperature, and 

 the effect of environment finds abundant ex- 

 pression in the great variety of fern struc- 

 tures." After palms, ferns form the most con- 

 spicuous feature of tropical vegetation, and in 

 size they vary from species only a fraction of 

 an inch high to splendid tree ferns or vines 

 single fronds of which are more than thirty 

 feet long. In texture " some rival the flim- 

 siest lace, while others develop thick, leathery 

 fronds. ... In habit the variation is fully as 

 great. In western Nicaragua, for example, 

 where there is a distinct dry season, ferns 

 growing on bare volcanic rock become so dry 

 that they may be ground to powder between 

 the fingers, and yet they retain life ; while in 

 the eastern part, with its deep jungles in 

 which perpetual shade and moisture prevail, 

 the more delicate as well as the more gor- 

 geous forms have full opportunity for the 

 development of their many peculiarities." 

 In a very small territory of Nicaragua, in- 

 cluding a strip along the San Juan River in 

 no case extending more than six miles away 

 from it, and in the little island of Ometepe 

 in Lake Nicaragua, Mr. Shimek, in less than 

 four months, while engaged in general bo- 

 tanical work, collected more than a hundred 

 and twenty species of ferns ; and yet only 

 about one fifth of one hundred and twenty- 

 one species recorded by Founder, two fifths 

 of one hundred and thirty-five species cred- 

 ited by Hemsley to Nicaragua, and two fifths 

 of those reported by Baker and Hemsley 

 from adjacent Costa Rica, occur in his list. 



Wave Length and other Measurements. 



— Describing the measurement of absolute 

 wave length before the Astronomical and 

 Physical Society of Toronto, Mr. A. F. Miller 

 remarked that a somewhat incorrect idea 

 prevailed as to the smallness of the space 

 occupied in the performance of luminous un- 

 dulations; in fact, some people seem to re- 

 gard the wave length of light as something 

 almost inconceivably small. Really, how- 

 ever, we are familiar with much smaller di- 

 mensions. For instance, the author had 

 found from actual measures that the wave 

 length of one of the characteristic lines in 

 the spectrum of sodium vapor was very nearly 



