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THE POPULAR SCIENCE MONTHLY. 



of sand were formed, several feet deep in 

 favorable places, packed as snow-drifts are 

 packed by a blizzard. In parts of the West- 

 ern plains the fine, loose sand has been 

 blown away at times, leaving every pebble 

 and large bowlder standing out in bold re- 

 lief. The loose material often gathers in the 

 form of drifts or dunes, which travel across 

 the country with frequent changes of out- 

 line. A few miles north of Winnemucca 

 Lake, in western Nevada, is a belt of these 

 drifting sand hills, described by the geolo- 

 gist Russell as some seventy-five feet in 

 thickness and about forty miles in length by 

 eight miles in breadth. Another range of 

 sand dunes, at least twenty miles long, and 

 forming hills some two or three hundred 

 feet high, is on the eastern end of Alkali 

 Lake in the same State. Dunes of equal 

 height have been formed on the eastern 

 shore of Lake Michigan, and at Grand Ha- 

 ven and Sleeping Bear have drifted over the 

 woodlands, so as to leave only the dead tops 

 of trees exposed. The erosive power of 

 these drifting sands is often an important 

 agent in wearing away the rocks upon which 

 they strike. Carried along by the force of 

 the winds, they work effectively in undermin- 

 ing cliffs, scouring down mountain passes, 

 and giving curious and fantastic forms to 

 prominent rocks. 



The Whistled Language of the Canary 

 Islands. — As a result of his studies of the 

 whistled language of Gomera, in the Canary 

 Islands, M. J. Lajard affirms that it is not a 

 special idiom or a whistle which tries to imi- 

 tate the Spanish language; but it is the 

 Spanish language strengthened by the aid 

 of whistling. " The Gomerian, while he is 

 speaking, puts one, two, or four fingers in 

 his mouth, as we sometimes see done in the 

 street in order to make shrill sounds, and at 

 the same time he whistles with force. There 

 results a mixture of words and whistle, un- 

 intelligible to ears not accustomed to it, but 

 in which can be distinguished the words of 

 the language. . . . The whistling, then, is 

 only an artifice employed to carry to a dis- 

 tance the sound of the voice, to the detri- 

 ment of its distinctness and tone-quality. 

 This last inconvenience is so great that up 

 to this time travelers have been unable to 

 understand the whistled language. To be 



able to understand it, you must know how 

 to whistle yourself." It is, however, very 

 limited in its compass, and whistled conver- 

 sations are of short duration. It exists in 

 other of the Canary Islands than in Go- 

 mera, and there is reason for believing that 

 it was formerly more widespread and more 

 prevalent than now. Rudiments of a whis- 

 tled language, the mechanism of which is 

 like that of the Canaries, exist even in 

 Paris; it is employed by butchers and by 

 thieves. 



What constitutes a Polluted Water. — 



A water is said to be polluted, according to 

 Prof, von Pettenkofer, when it is no longer 

 clear and inodorous, when fishes and plants 

 perish in it, and when it contains more 

 organic matter and less oxygen than are to 

 be found in the unpolluted portions of the 

 flow of the stream. Such contamination is 

 essentially different from the transient tur- 

 bidity due to heavy rains or to melting snow. 

 Still, even the permanent pollutions disappear 

 in the further course of the river bed, by 

 deposition and other agencies. Here the 

 rapidity of the stream and the quantity of 

 the water exert a preponderating effect. The 

 most formidable impurities are supposed to 

 consist of the putrescent refuse which flows 

 out of sewers of cities, and quickly produces 

 an offensive odor at the places where it 

 accumulates. Prof, von Pettenkofer has for 

 many years given his attention to the ques- 

 tion of the extent to which rivers are polluted 

 by such agencies, and has had researches 

 conducted by his pupils. But nothing has 

 hitherto altered the opinion which he ex- 

 pressed long ago, that sewage may be safely 

 permitted to flow into a river if its volume 

 is not more than one fifteenth that of the 

 river water, and its rate of flow is decidedly 

 greater than that of the current. Taking the 

 city of Munich, which has 280,000 inhabi- 

 tants, he computes the pollution of the Isar 

 by its sewage as amounting to only Tiro owd" 

 of the discharge of the river — a pollution so 

 inconsiderable that it can not be detected by 

 the eye when a corresponding mixture is made 

 up experimentally. But it is also not perma- 

 nent, for at Ismaning, seven kilometres below 

 Munich, the sewage influx is no longer to be 

 detected ; and at Freising, thirty-three kilome- 

 tres below, the chemical and bacteriological 



