May 2nd, 1887.] 



SCIENTIFIC NEAVS. 



55 



does not give out energy continuously at the rate of a 

 horse-power, or anything like it. To illustrate his meaning, 

 he said that if a man goes to a shop and buys a watch, his 

 expenditure for the moment when his money passes over 

 the counter may be at the rate of ^100, 000 a year, but it by 

 no means follows that his spending capacity is _;^ioo,ooo a 

 year because it attains that rate for an instant. Similarly, 

 it does not follow that a horse-power-hour cell will give out 

 the energy of a horse-power for an hour, merely because it 

 attains that rate for a short time. Professor Ayrton there- 

 fore urged that a statement should be made of the number 

 of Watts that can be obtained from a cell for a given 

 expenditure of money, say ;£i. 



The Bark of the Mulberry Tree as a Textile. — A 

 few weeks ago a company was started in Italy for produc- 

 ing silk, so-called, direct from the bark of the mulberry tree. 

 The promoters of this company, after patenting their inven- 

 tion, went to France, and, having explained the matter to 

 some of the French papers, articles were written on the 

 subject, which excited considerable interest amongst those 

 engaged in the silk industry. It was feared that, by means 

 of this discovery, and the patent taken out on the strength 

 of it, a new monopoly would be established, but on examin- 

 ing the question more closely it is found that the idea was 

 not altogether new. M. Ponsard has written to an agricul- 

 tural paper (Lc Journal d' Agriculture Pratique) stating that 

 in 1882 he successfully tried the process, and, further, that 

 the method of working is fully described in a book published 

 in 1804, and written by M. Olivier de Serres. A reference 

 to this book, the title of which is " Theatre d'Agriculture 

 et Menage des Champs," shows that on pp. 147 to 151 

 there is, among other descriptions of useful and interesting 

 applications of the mulberry tree, an account of the way in 

 which silk may be obtained from the bark. The silk thus 

 obtained is finer than cotton wool and flax, but is not equal 

 to ordinary silk. 



Why Paper Turns Yellow. — All paperwill turn yellow finally 

 if time enough be given. Against this change we are powerless. 

 When, however, a paper will not retain its original white colour 

 for a few weeks, or even days, we have reason to complain ; and 

 we may assume in such a case that a wood-pulp has been used ; 

 not a wood-pulp prepared chemically by means of acids or caus- 

 tics, but a wood-pulp obtained simply by mechanical operations, 

 by grinding, etc. According to recent experiments of Julius 

 Wiesner, of Vienna, the cause of this change is not so much light, 

 as oxygen, to which almost every fault is now charged. Chips 

 of paper placed in the vacuum over the mercury, in a barometer 

 tube, kept perfectly white, even when water was present. But 

 exposed to the direct sunlight in the air, the paper turned rapidly ; 

 and a strong sunlight was found very much more dangerous than 

 ordinary dilfuse light ; moisture is also pernicious. A further 

 examination with coloured rays proved that the blue actinic rays, 

 particularly active in photography, are mainly responsible for 

 this change. Gaslight is poor in these rays ; and, indeed, a 

 sheet of a newspaper illuminated by a gas flame which was kept 

 burning day and night for a whole month, had hardly any yellow 

 tint at all ; and when this test had been continued for four 

 months, the paper still looked whiter than another sheet of the 

 same paper exposed to the full sunlight for two hours. Since 

 the electric arc has many actinic rays it follows that the arc- 

 lamp is not the best illuminant for a library. The readers of 

 the British Museum would be pleased if the authorities were 

 guided by these facts, for few would be sorry to see gas substi- 

 tuted for the present trying arc-lights, with their strong contrasts 

 of light and shade. But if gaslight does not turn paper yellow, 

 it has that effect on other things. Wiesner's experiments help 

 to clear up the difference existing in this respect between chemi- 

 cally and mechanically prepared wood-pulp. The chemical treat- 

 ment destroys certain bodies, which the mechanical treatment 

 leaves intact. Amongst these bodies are vanillin, coniferin, and 

 various gums. Coniferin is entirely decomposed by light, as also 

 is vanillin to a great extent. Jute and straw papers, being not 

 always free from these substances, may also turn yellow. 



DOMESTIC SANITATION. 



No. I. — Water Supply. 



IT must be conceded that national and local authorities 

 often commit grievous errors in dealing with questions 

 of public health. But the wisest sanitary laws must prove 

 inefficient unless the individual householder has an intelli- 

 gent insight into the main principles of hygiene, and if he 

 will not act up to such insight. After all our vaunts about 

 " progress," the sanitary code laid down in the Pentateuch 

 should still be far in advance, not, indeed, of our modern 

 knowledge, but of our modern practice. 



We purpose, therefore, laying before our readers a brief 

 series of papers on household hygiene. We shall not 

 attempt to give instructions in the analysis of water and 

 air, or to qualify paterfamilias for the duties of a medical 

 officer of health or a sanitary inspector, but we shall point 

 out possible sources of danger and necessary precautions, 

 both of which are too often overlooked, and do what we 

 can towards forming, on this subject, an enlightened public 

 opinion. 



The first, and perhaps the most important, point to be 

 considered is the water supply, since water may be, and 

 too often is, the channel through which disease and death 

 are introduced into a family. 



It may, perhaps, be thought that since the increasing 

 density of population and the accompanying pollution of 

 the soil and the streams have in most parts done away with 

 private pumps and wells, the individual has here little 

 power, and must simply use whatever fluid is supplied to 

 him by a company, or, in the best case, by the municipal 

 authority. But this is not so ; he can often in choosing 

 his residence be guided by the character of the water, or 

 else he can join the agitations for improvement in the 

 quality, such agitations, as public opinion is gradually 

 enlightened, will become irresistible. 



The first question concerning water is its quality. Is it 

 hard or soft ? It is not to the credit of medical science 

 that in connection with this question there is a striking 

 diversity of opinion. Some authorities maintain that hard 

 waters are preferable for dietetic purposes as supplying the 

 mineral salts which are required in the animal system, and 

 especially in the formation of the bones. They contend 

 that the inhabitants of calcareous districts, where the 

 waters are necessarily hard, are bigger, stronger, freer from 

 disease, and live longer than the dwellers on such forma- 

 tions as the granite or the mill-stone grit, where the waters 

 are soft. 



The champions of soft water, on the other hand, argue 

 that the finest specimens of modern Englishmen are to be 

 found in the "back-bone" of England and the adjoining parts 

 of Yorkshire and Lancashire, where the grit-stone formation 

 yields copious springs of the softest water, fed by the very 

 abundant rain-fall. They denounce hard water as being 

 one of the secondary causes of diarrhoea, cholera, and 

 calculi. 



But the impartial observer will not feel fully satisfied 

 with the evidence on either side. The death-rate in towns, 

 supplied respectively with hard and soft water, does not 

 vary so strikingly and regularly as to lead to any definite 

 conclusion. And so many other factors have to be taken 

 into account that statistical returns can scarcely be expected 

 to decide the question. 



Soft waters have, however, in many respects an un- 

 questionable superiority. In washing the human person 

 or linen, etc., they remove dirt with a very triOing ex- 

 penditure of soap, and leave the surface clean and free 

 from clamminess. Compare this with the process of wash- 



