144 



THE POPULAR SCIENCE MONTHLY. 



that a soil is a laboratory and not a mine, is 

 erroneous ; for not only the facts adduced 

 by them in previous papers, but the whole 

 history of agriculture, so far as we know it, 

 show that a fertile soil is one which has 

 accumulated within it the residue of ages of 

 previous vegetation, and that it becomes less 

 fertile as this residue is exhausted. 



Dr. Cobbold, an eminent authority on 

 the subject, asserts that the danger of eat- 

 ing parasites in lish used as food is much 

 exaggerated, and that there is extremely 

 little of it. If the fish are only moderately 

 boiled, the parasites will all be killed, and, 

 if they are not, not one in a thousand of 

 them will find itself at home enough in the 

 lumian stomach to do any harm. Professor 

 Huxley also declares that the thread-worm 

 of the mackerel is harmless, and that the 

 idea of its being a possible cause of cholera 

 is sheer nonsense ; and he thinks it outra- 

 geous that the suggestion ha^ been made. 



Masks of mica are made at Breslau for 

 the use of workmen who are exposed to 

 high temperatures, to acid vapors, or to 

 metallic sparks. They are found to protect 

 the eyes better than glasses, while there is 

 space enough between them and the eyes to 

 permit spectacles to be used also. The 

 plates of mica are fixed in metallic supports 

 protected with amianthus, and the neck and 

 shoulders of the workman are covered with 

 a hood of that substance. 



The Eilsitt bridge, Lyons, France, is 

 called " the singing-bridge," on account of 

 the musical sounds it emits at different parts 

 of its course, " when at particular moments 

 one might believe it haunted by legions of 

 invisible naiads pursuing the passengers 

 with their plaintive melodies." The bridge 

 is furnished with a stone parapet, which is 

 pierced at intervals for light, with rectangu- 

 lar openings having their ends rounded oif 

 in semicircles. The effect of this passage, 

 with the air-currents rushing through it, is 

 that of a flute, of which the windows rep- 

 resent the holes. The tones vary considera- 

 bly at times in intensity, with but little differ- 

 ence in their pitch. 



Thk prairie-wolf has been introduced 

 into Epping Forest, England, and appears 

 to be breeding freely there. The animals 

 have been confounded by some persons with 

 cubs of the fox, and described by others as 

 " strange animals from foreign parts." One 

 of them was recently offered to Mr. Bartlett, 

 Superintendent of the London Zoological 

 Gardens, who, doubting whether it might 

 not be a hybrid of some kind, visited the 

 forest to learn something more about its 

 real character. The less frequented parts 

 of the forest seem well suited to the habits 

 of the animals, and they promise to thrive. 



Dr. Richardson has sounded a note of 

 warning against the too hasty and complete 

 acceptance of the bacillus theory for the 

 origin of every kind of infection, to the 

 neglect "of all the preceding clinical his- 

 tory." He asks : " Upon the evidence of how 

 many or how few men does the bacillus hy- 

 pothesis rest? On what reasoning does it 

 rest ? Who has separated, in relation to it, 

 coincidence from causation '? " To ask these 

 questions, or to heed them, is not necessarily 

 to question the validity of the bacillus the- 

 ory, but simply to pause and review, and 

 ask for the proof of it. 



The question whether the water of a 

 river like the Thames, when once polluted 

 by sewage, can be made fit for drinking pur- 

 poses, either by the oxidation incident to its 

 own flow or by artificial filtration, was again 

 up for discussion recently before the Lon- 

 don Society of Arts. Dr. Frankland took the 

 negative side upon it, and insisted that the 

 Thames's supplies to London should be aban- 

 doned ; while many eminent engineers and 

 a few chemists positively contradicted both 

 his data and his conclusions. Mr. W. Mat- 

 tieu Williams suggests that the force of the 

 latter gentlemen's opinions is somewhat de- 

 tracted from by the fact that most of them 

 are concerned in the construction of filter- 

 beds and other engineering appliances for 

 river-water purification, or in schemes for 

 chemical precipitations. 



The ice-plant of our ladies' window-bas- 

 kets {Mesembryanthcmum crystallinuni) af- 

 fords a striking illustration of the elective 

 power which plants have of taking up by 

 their roots from a complex soil the materials 

 proper for them. M. Mangon has cultivat- 

 ed it for several years on the same ground 

 with cabbage, celery, and other plants, and 

 has found that, while the latter plants had 

 their normal composition, the ice-plant, dried 

 and burned, furnished an ash with an amount 

 of chlorine and alkali that astonished him. 

 From one hectare, or two acres and a half 

 of ice-plants, he obtained 1,820 kilogrammes 

 of ashes, containing 335 kilogrammes of chlo- 

 rine, as much soda, and 588 kilogrammes of 

 potash, the latter of which substances was 

 capable of furnishing 86^ kilogrammes of 

 carbonate of soda, or nearly as much as is got 

 from the incineration of one hectare's yield 

 of the salt-works at Alicante. M. Mangon 

 suggests that this plant might be cultivated 

 for a potash-plant, and that it might be made 

 serviceable in removing the excess of alka- 

 line salts from salt grounds. 



A correspondent of " Nature " writes 

 from Java that, having recently killed one 

 of the venomous snakes of that island, he 

 noticed the tail of a second snake sticking 

 from its mouth, and found that it had 

 swallowed another individual of the same 

 species, and nearly the same size with itself. 



