176 



POPULAR SCIEI^CE I^EWS. 



[December, 1888. 



ranges between 105° and 113°, which is the neces- 

 sary temperature to kill the bacilli. 



M. Krull recommends a similar method, but 

 the temperature of the air must not exceed 115°. 

 Upon the whole, nothing is known of the positive 

 effects of these methods. M. Dettweiler of the 

 Falkenstein Sanatorium has recently published 

 (F. Alcan, publisher, Paris) a very interesting 

 brochure on the method followed in his Sanatorium, 

 which is exclusively devoted to tuberculous pa- 

 tients. The main points of the method are to oblige 

 the patient to live in the open air under all circum- 

 stances, and to sleep in open halls or on verandas, 

 however cold it may be (23° and 14° F. !). The 

 great point is to have the patient always breathe 

 pure air. The temperature seems to have no in- 

 fluence, since the results are the same in summer 

 and in winter; and as the patients are well covered, 

 to prevent chill and cold, they become rapidly 

 accustomed to the method, and feel so much 

 improved, that they like it greatly. The proportion 

 of successful cases is twenty-five per cent, and the 

 perusal of M. Dettweiler's brochure is really very 

 interesting. 



M. Hallez of Lille has recently published a 

 very interesting note concerning the different ani- 

 mals which fulfil the duties of scavengers of the 

 sea-beach, and destroy all animal corpses and 

 vegetable detritus which are washed up by the sea, 

 or brought by rivers. Even at very short distances, 

 the scavengers are of quite different sort: in one 

 place it is the genus Nassa ; in another a crustacean, 

 Eurydice pulchra, or species of Ligia and Orchestia. 



A STATUE of Ampferehas been recently unveiled, 

 and a new sanatorium for scrofulous and tuber- 

 culous children opened in Banyulis-sur-Mer, on the 

 Mediterranean. 



V. 



Oct. 23, 1888. 



THE NUMBER OF THE STARS. 



The total number of stars one can see will 

 depend very largely upon the clearness of the 

 atmosphere and the keenness of the eye. There 

 are in the whole celestial sphere about 6,000 stars 

 visible to an ordinarily good eye. Of these, how- 

 ever, we can never see more than a fraction at any 

 one time, because a half of the sphere is always 

 below the horizon. If we could see a star in the 

 horizon as easily as in the zenith, a half of the 

 whole number, or 3,000, would be visible on any 

 clear night. But stars near the horizon are seen 

 through so great a thickness of atmosphere as 

 greatly to obscure their light, and only the bright- 

 est one< can there be seen. As a result of this 

 obscuration, it is not likely that more than 2,000 

 stars can ever be taken in at a single view by any 

 ordinary eye. About 2,000 other stars are so near 

 the South Pole that they never rise in our latitudes. 

 Hence, out of 6,000 supposed to be visible, only 

 4,000 ever come within the range of our vision, 

 unless we make a journey towards the equator. 



As telescopic power is increased, we still find 

 stars of fainter and fainter light. But the number 

 cannot go on increasing forever in the same ratio 

 as with the brighter magnitudes, because if it did 

 the whole sky would be a blaze of starlight. If 

 telescopes with powers far exceeding our present 

 ones were made, they would no doubt show new 

 stars of the twentieth and twenty-first, etc., mag- 

 nitudes. But it is highly probable that the number 

 of such successive orders of stars would not in- 

 crease in the same ratio as is observed in the eighth, 

 ninth, and tenth magnitudes, for example. The 

 enormous labor of estimating the number of stars 

 of such classes will long prevent the accumulation 



of statistics on this question; but this much is 

 certain, that in special regions of the sky, which 

 have been searchingly examined by various tele- 

 scopes of successively increasing apertures, the 

 number of new stars found is by no means in pro- 

 portion to the increased instrumental power. If 

 this is found to be true elsewhere, the conclusion 

 may be, that, after all, the stellar system can be ex- 

 perimentally shown to be of finite extent, and to 

 contain only a finite number of stars. In the whole 

 sky an eye of average power will see about 6,000 

 stars, as I have just said. With a telescope this 

 number is greatly increased, and the most powerful 

 telescopes of modern times will show more than 

 60,000,000 stars. Of this number, not one out of 

 one hundred has ever been catalogued at all. . . . 

 In all, 314,926 stars, from the first to the ninth 

 and a half magnitude, are contained in the north- 

 ern sky, or about 600,000 in both hemispheres. 

 All of these can be seen with a three-inch object- 

 glass. — Professor E. S. Holden, in the August 



Century. 



— »^ 



SPIDERS' WEBS. 



I READ a statement in this magazine Hot long 

 ago, about the spiders' webs that cover the fields 

 and meadows on certain mornings in the summer, 

 which was not entirely exact. It is not quite true, 

 in the sense in which it was uttered, that these 

 spiders' webs are more abundant on some morn- 

 ings than on others, and that they presage fair 

 weather. Now, the truth is, that during the latter 

 half of summer these webs are about as abundant 

 at one time as at another; but they are much more 

 noticeable on some mornings than on others, — a 

 heavy dew brings them to view. They are espe- 

 cially conspicuous after a morning of fog, such as 

 often fills our deeper valleys for a few hours when 

 fall approaches. They then look like little napkins 

 spread all over the meadows. I saw fields last 

 summer in August when one could step from one 

 of these dew-napkins to another for long distances. 

 They are little nets that catch the fog. Every 

 thread is strung with innumerable fine drops, like 

 tiny beads. After an hour of sunshine the webs 

 apparently are gone. 



Most country people, I find, think they are due 

 to nothing but the moisture; others seem to think 

 that the spiders take them in as morning ad- 

 vances. But they are still there, stretched above 

 the grass at noon and at sunset, as abundant as 

 they were at sunrise, and are then more serviceable 

 to the spiders, because less visible. The flies and 

 insects would avoid them in the morning, but at 

 midday they do not detect them so readily. 



If these webs have any significance as signs of 

 the coming weather, this may be the explanation : — 



A heavy dew occurs under a clear, cool sky, and 

 the night preceding a day of rain is usually a dew- 

 less night. Much dew, then, means fair weather, 

 and a copious dew discloses the spiders' webs. It 

 is the dew that is significant, and not the webs. — 

 John Burroughs, in Si. Nicholas. 



SCIENTIFIC BREVITIES. 



Preservation of Desmids. — It is stated by 

 W. Migula that desmids and other species of fresh- 

 water algae may be preserved for microscopic 

 mounts, with the complete prevention of proto- 

 plasmic contraction, by treating them first with a 

 one per cent solution of perosmic acid for from ten 

 to twenty minutes, and then placing them in a con- 

 centrated solution of potassium acetate, for mount- 

 ing or for permanent preservation. 



The Signal Service. — Gen. Greely, in his 

 annual report, says that the percentages of- success- 

 ful weather-predictions made by the signal oflice 



for the year were 78.4; wind, 75 5; temperature, 

 74.2; general average, 76.7. The number of cold- 

 wave signals displayed was 1,743, of which 1,240, 

 or 71.5 per cent, were verified. 



A Leather- Wo-RM. — Professor Riley, the emi- 

 nent entomologist, has discovered an insect which 

 preys upon boots and shoes. The pest can be de- 

 stroyed by a vapor of bisulphide of carbon. 



Quicksand. — Quicksand is composed chiefly of 

 small particles of mica mixed largely with water. 

 The mica is so smooth, that the fragments slip upon 

 each other with the greatest facility, so that any 

 heavy body which displaces them will sink, and 

 continue to sink, until a solid bottom is reached. 

 When particles of sand are ragged and angular, any 

 weight pressing on them will crowd them together 

 until they are compacted into.a solid mass. A sand 

 composed of mica or soapstone, when sufiiciently 

 mixed with water, seems incapable of such consoli- 

 dation. 



Electric Heat Indicators, consisting of ther- 

 mometers incased and protected by iron tubes, pro- 

 vided with platinum wires, and connected to a sys- 

 tem of electric bells and indicators on deck, are the 

 latest invention for preventing spontaneous combus- 

 tion among ship cargoes. Should any undue heat 

 arise in any part of the cargo, the mercury in the 

 thermometers will rise, make contact with the plati- 

 num wire, and give an instantaneous alarm on deck, 

 indicating at the same time the exact spot where 

 the heat exists. 



The First Lightning-Rod. — If we are to be- 

 lieve an Austrian paper, says La Lumiere Electrique, 

 the first lightning-rod was not constructed by Frank- 

 lin, but by a monk of Seuftenberg, in Bohemia, 

 named Prohop Diwisch, who installed an appa- 

 ratus the 15th of June, 1754, in the garden of the 

 curate of Prenditz (Moravia). The apparatus was 

 composed of a pole surmounted by an iron rod sup- 

 porting twelve curved-up branches, and terminat- 

 ing in as many metallic boxes filled with iron ore 

 and closed by a boxwood cover, traversed by twen- 

 ty-seven sharp iron points, which plunged at their 

 base in the ore. All the system was united to the 

 earth by a large chain. The enemies of Diwisch, 

 jealous of his success at the court of Vienna, excited 

 the peasants of the locality against him, and, under 

 the pretext that his lightning-rod was the cause of 

 the great drought, they made him take down the 

 lightning-rod which he had utilized for six years. 

 What is most curious is the form of this first light- 

 ning rod, which was of multiple points, like the 

 one which M. Melseu afterwards invented. 



Cliff Dwellings in Morocco. — Recent dis- 

 coveries have shown that cliff dwellings are found 

 in great numbers in Morocco, which are now, aid 

 probably have been, inhabited from tlie time of 

 their first construction. These dwellings in all 

 particulars are like those found in Arizona and 

 New Mexico on this continent. A New York paper 

 speaks of them as follows: " It was not until last 

 year that the Moors would permit any examination 

 of the cliff dwellings which have long been known 

 to exist some days' journey south-west of the city 

 of Morocco. The strange city of the cave-dwellers 

 is almost exactly like some of those in New Mex- 

 ico and other territories, which archseologists have 

 explored. The dwellings were dug out of the 

 solid rock, and many of them are over two hundred 

 feet above the bottom of the valley. The face of 

 the clifl is, in places,- perpendicular; and it is be- 

 lieved that the troglodytes could have reached their 

 dwellings only with the aid of rope-ladders. Some 

 of the dwellings contain three rooms, the largest 

 of which are about seventeen by nine feet, and 

 the walls of the larger rooms are generally pierced 

 by windows. Nothing is known as to who these 

 cave-dwellers were." 



