116 



POPULAR SCIEITCE l^EWS. 



[August, 1888. 



in their habits, frequently going out at night in 

 search of prey. It is stated that the Californian 

 " cork " spider (Cleniza Californica) fastens its door 

 open with a silken thread before leaving its nest, 

 the door being so difficult to open from the outside. 

 The greatest enemies of trap-door spiders in 

 Europe are lizards and centipedes, and the spiders 

 are always on the alert to guard against their at- 

 tacks ; so that, if the outer door of a double-door 

 nest be opened, the spider immediately slams the 

 inner door to, for fear of its pursuers. If the latter 

 be forced open or removed, the spider will generally 

 flee to the very bottom of her nest, where she will 

 be found crouched up in terror. Owing to the 

 complete concealment which the doors of the nests 

 effect, the only way of detecting them in countries 

 where trap-door spiders abound is to turn up all 

 the likely-looking bits of earth until one of the 

 nests is found. — G. H. Bryan, in Journal of 



Microscopy. 



—* — 



THE GflAND MAGNET AT WILLETT'S 

 POINT. 



Last December Major King happened to see two 

 large fifteen-inch Dahlgren guns lying unused side 

 by side on the dock. He immediately conceived 

 the idea that a magnet of enormous power could 

 be constructed by means of these cannon, with 

 submarine cable wound about them. The experi- 

 ment proved very successful. The magnet, which 

 stands about ten feet from the ground, is eighteen 

 feet long, and has eight miles of cable wound about 

 the upper part of the guns. It is the largest and 

 most powerful magnet in the world. Some faint 

 idea of its power may be conceived from the fact 

 that it takes a force of twenty-five thousand pounds 

 to pull off the armature. A crowbar which was 

 applied to the magnet required the combined force 

 of four strong men to tear it away. A handful of 

 pins thrown in the opposite direction immediately 

 flew back, and attached themselves to the magnet. 

 A seemingly impossible experiment was performed 

 with some fifteen-inch cannon-balls. The balls were 

 solid, and as much as a strong man could lift ; yet 

 the magnet held several of them suspended in the 

 air, one under the other. 



The. most interesting experiment was the test 

 made of an American non-magnetic watch. Ever 

 since the great railroads of the country have com- 

 pelled their employees to provide themselves with 

 timepieces that would not be affected by the mag- 

 netism generated by the car-trucks, there has been 

 much speculation as to whether such a watch could 

 be made, and a sharp rivalry has been going on 

 between the American and Swiss manufacturers. 

 The test was highly satisfactory, and once more 

 proved that, whenever a new invention was impera- 

 tively demanded, American genius could fully hold 

 its own against the whole world. Major King's 

 magnet was so powerful, that an ordinary watch 

 was stopped stock still as soon as it came within 

 three feet of it. Before the test was made, there 

 was quite a diversity of opinion among the experts 

 present as to how far it would prove successful. 



Those who believed that a watch might be 

 constructed that would resist magnetic influence 

 under ordinary circumstances, were also of the opin- 

 ion, that, when it was subjected to the most power- 

 ful magnet in the world, the steel pinions would 

 bear so on the working parts, that the watch must 

 necessarily stop. For ten minutes the watch was 

 held in front of the magnet. It did not vary the 

 hundredth part of a second. The man who held it 

 said that he himself was conscious of the influence 

 of the magnet. He could feel, as he held the watch 

 by the chain, that some other power than his was 

 keeping it suspended. The most amusing experi- 

 ment was made with a sledge-hammer. When one 



tried to wield it in a direction opposite to the mag- 

 net, he felt as though he were trying to hit a blow 

 with a long feather in a gale of wind. There is 

 nothing in the world that could take the conceit 

 out of a strong man so much as this simple experi- 

 ment Another amazing test was made with a 

 number of carpenter's spikes. A spike was put 

 lengthwise on the end of the magnet, then another 

 spike was attached to the first, and so on until a 

 line of them stood straight out from the magnet at 

 least four feet in length. — New York Sun. 



AN UNPOLISHABLE DIAMOND. 



A REMARKABLE diamond was exhibited at a 

 recent meeting of the New York Academy of 

 Sciences by Jlr. George F. Kuntz. It was a 

 compound or multiple crystal, containing a large 

 number of twinnings. It is of the class termed 

 "extreme durate" by the French. It had been 

 cut into the general shape of a brilliant, and its 

 main face or table was then placed on the polishing 

 wheel. It was kept there for a hundred days, the 

 wheel revolving at the rate of 2,800 revolutions per 

 minute. The diamond was held upon the rotating 

 surface at a distance of about 15 inches from the 

 centre. Based on these figures, a calculation 

 showed that the surface passed over by the diamond 

 amounted to 75,000 miles, or nearly three times 

 the circumference of the earth. Yet it was all 

 futile, as the stone would not acquire a polish. 

 The ordinary weight placed on a diamond while 

 on the whpel is from 2^ to 2J pounds. This was 

 increased by 4 and 8 pounds without effect, and 

 finally 40 pounds were used. The wheel was 

 badly damaged, the diamond ploughing into it, and 

 throwing scintillations in all directions. The dia- 

 mond, even under these conditions, could not be 

 given a commercial polish. The wheel had to 

 be replaced. — Scientific American. 



SCIENTIFIC BREVITIES. 



Dangerous Photography. — An attempt was 

 recently made in Dublin to photograph a lioness 

 with the head of the tamer in its mouth. The 

 animal, wearied by the tension of her maxillary 

 muscles, or scared, it may be, by the sudden flash 

 of the magnesium light, tore the woman's cheek 

 completely open. Fortunately, no more serious 

 injury resulted, the lioness being beaten off in time 

 to prevent a threatened catastrophe. 



The Moon's Heat. — From observations upon 

 the total lunar eclipse of last January, Professor 

 Boedicker found — 



That the heat radiated by the moon begins to 

 decrease a considerable time before the first con- 

 tact with the penumbra. 



That 22 minutes before the beginning of totality 

 the heat is only 4.7 per cent of the value obtained 

 1 hour and 10 minutes before the first contact with 

 the penumbra. Unfortunately, an unforeseen stop- 

 pageof the driving-clock prevented the observations 

 from being carried on closer up to and during the 

 total phase. 



That, in spite of the rapid fall on approach to 

 totality, the heat, after the last contact with the 

 penumbra, does not at once increase to any thing 

 like the value observed at corresponding times 

 before the first contact. 



Natural Gas. — ■ Analysis of natural gas shows 

 the proportion of each constituent in 100 parts of 

 the gas to be as follows : Carbonic acid and carbonic 

 oxide, -fg each; oxygen, j^^ ; defiant gas, 1; 

 ethylic hydride, 5; marsh gas, 67; hydrogen, 22; 

 nitrogen, 3. 



The Principal Languages. — It has been esti- 

 mated by Professor KirchhofE of Halle that the 



language most spoken on the globe — for the last 

 thousand years, at least — is Chinese, for it is with- 

 out doubt the only one which is talked by over 

 400 millions of the human race. The next lan- 

 guage most in use — but at a very great distance 

 behind Chinese — is Hindustani, spoken by over 

 100 millions. Then follow English (spoken by about 

 100 millions), Russian (over 70 million.s), German 

 (over 57 millions), and Spanish (over 47 millions). 



Crookes's Radiometer is being used in France 

 for timing the exposure of photographic plates; 

 an equal number of revolutions of the vanes of this 

 little instrument corresponding to the proper time 

 of exposure, whatever the degree of brightness of 

 the light. 



Professor Wolcott Gibbs has resigned the 

 Rumford Professorship in Harvard University in 

 order to devote himself exclusively to research. 

 He has removed to Newport, R I., where he is 

 erecting a private laboratory. 



The Atomic Weight of Antimony. — Pfeiffer 

 and Popper have proceeded by the electrolysis of a 

 solution of antimonious chloride, and have obtained 

 the values 120.72, 120.82, and 12054, — figures 

 which are a unit higher than the value found by 

 Cooke. 



A ''Woolly Crocodile." — A curious crea- 

 ture is said to have been brought to San Francisco 

 by a ship which arrived there the other day. It has 

 some characteristics of the crocodile, but is covered 

 with a coat of short bristles or hair, which gives 

 it a most peculiar appearance. It has been domes- 

 ticated to a certain extent, and will permit the cap- 

 tain or any of the crew to approach it, and receives 

 their caresses with evident pleasure ; but if a 

 stranger approaches, it distends its big jaws, and 

 shows fight. The crew call it a " woolly crocodile." 

 It is active, and weighs about forty pounds. 



An Ancient Process for Rendering Jewels 

 Phosphorescent. — The collection of the Greek 

 alchemists found in certain MSS. of the thirteenth 

 and fifteenth centuries in the National Library 

 describes processes used for the artificial coloration 

 of factitious jewels, emeralds, carbuncles, and hya- 

 cinths. Stones were to be made luminous in the 

 night by dyeing them with a mixture of copper- 

 rust and of the gall of the tortoise. A finer color 

 was obtained by using the sea medusa instead of 

 the tortoise. This coloration was, of course, not 

 permanent; but it was easily reproduced 



Snow from a Clear Sky. — On Jan 3 snow fell 

 in Christiania from a perfectly clear sky. After 

 a strong southerly wind, with cloudy weather in the 

 morning, the weather cleared, but at about noon it 

 again thickened, and snow and sleet fell. In the 

 afternoon the sky again became clear, and continued 

 thus, with a storm blowing from the west. Just be- 

 fore eight P.M., however, thick clouds again gath- 

 ered, the full moon became obscured, and snow 

 began to fall heavily. A quarter of an hour later 

 the wind swept the clouds away, and the sky be- 

 came completely clear, with the exception of a few 

 clouds in the east. The stars shone brightly, and 

 the full moon illuminated the landscape; still snow 

 continued to fall thickly for some ten minutes. 

 That the snow could not have originated with the 

 clouds in the east, is proved by the circumstance 

 that the wind was westerly. A well-known meteo- 

 rologist ascribes the phenomenon to the presence, at 

 a certain elevation in the atmosphere, of a very cold 

 layer of air, in which the ascending comparatively 

 warmer air became condensed ; the moisture being 

 thrown out in the form of snow, but not in suffi- 

 cient quantities to obscure the blue sky, the stars, 

 and the moon. The great chilling of the layer of 

 air refened to may have been caused by the cold- 

 ness of the heavy snow-clouds which a few minutes 

 previously filled the atmosphere. 



