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SCIENTIFIC NE^A/^S. 



[June I, 1 888. 



a kind which keeps up a vigorous evaporation, and thus 

 promotes rainfall. 



In support of his contention, he shows that watery 

 vapour rarefies the atmosphere instead of, as now 

 supposed, increasing its specific gravity — a fact which, 

 as it is incidentally mentioned, explains why the baro- 

 metric measurement of the height of mountains generally 

 proves a failure, even in the most experienced hands. 

 Over dried-up land there seems to lie a drj' air-cushion, 

 unless the exhalation of moisture from vegetation pro- 

 motes a circulation in the layers of the atmosphere, thus 

 enabling the moist air of the upper regions to approach 

 the surface and come down as rain. Mr. Velschow 

 maintains that the Australian vegetation has a low degree 

 of evaporating power, and that to this circumstance is 

 due the irregularity of the rainfall. An improvement 

 would be possible if a vegetation having a high degree of 

 evaporating power could be superadded to, or to some 

 extent substituted for, the existing flora. No one cer- 

 tainly would complain if the Spinifex were displaced. 

 Our author proposes the experiment of planting belts of 

 deciduous trees extending gradually from the coasts 

 towards the interior. 



We may now glance at some facts which tell in favour 

 of Mr. Velschow's theory. We need not attempt to 

 prove that the countries forming the Mediterranean 

 basin — those especially at its eastern and southern 

 boundaries — have become less fruitful and populous than 

 was formerly the case, and that they have simul- 

 taneously been disforested. Now, as the decreasing 

 fertility is closely connected with a diminished rainfall, 

 and occurs only where water is absent, there is at least 

 prima facie evidence that the destruction of the woods 

 has been the cause of the mischief. 



On the other hand there are facts which, to us, seem 

 to speak on the opposite side. There are two belts 

 of droughty land running round the earth, one in either 

 hemisphere, interrupted only where they are intersected 

 by high mountain-chains, by great rivers, or by the sea. 

 The northern zone may be traced in the south-western 

 States of the American Union, especially the regions 

 formerly pertaining to Mexico. On this side of the 

 Atlantic it reappears in Africa, forming the Sahara, 

 passing over into Arabia and Persia, and then turning 

 mainly into Central Asia, although certain regions of 

 India sadly require a more ample and more regular rain- 

 fall. 



In the southern hemisphere we find an analogous 

 zone. It is strongly manifested on the western slope of 

 the Andes, in Chili, Bolivia, and Peru ; it extends east- 

 wards over a great part of the Argentine territory ; we 

 meet it again in Southern Africa, and lastly in Australia. 

 Now, it must seem strange that if these " rainless " tracts 

 depend on any peculiarity of the vegetation, they should 

 encircle the globe with such regularity. 



Mr. Velschow mentions the absence of lofty mountain 

 ranges in Australia as being a circumstance in favour of 

 a copious and regular rainfall in Australia. This, to say 

 the least, is a very doubtful point. We hope that the 

 author's theory may prove correct, and we should 

 strongly advocate the experimental plantings which 

 he recommends. It is to be noted that Baron Von 

 Miiller, botanist to the Colonial Government of Victoria, 

 recommends that the deserts should be attacked by 

 pushing forward belts of fig-trees, followed up by less 

 hardy plants, but the fig-tree gives off very little water 

 from its broad, leathery leaves. 



Natures Hygiene : A Systematic Manual of Natural 

 Hygiene, containing the Chemistry and Hygiene of 

 Eucalyptus, Pine and Camphor Forests, and Indus- 

 tries connected therewith. By C. T. Kingzett, F.I.C., 

 F.C.S. Third edition. London : Bailliere, Tindall, 

 and Cox. 

 The first edition of this work was devoted mainly to an 

 exposition of the sanitary efficacy of the eucalyptus, the 

 pines, camphor, and the essential oils, as well as to the 

 process of the manufacture of" sanitas" by oxidation. In 

 the second and in the present edition we find also 

 chapters on water supply, sewage, infectious diseases, 

 and the treatment of the sick, thus forming a general 

 sanitary manual. These subjects the author for the 

 most part treats in a very able and judicious manner. He 

 sets out with an exposition of chemical principles. He- 

 describes some of the more important elements and their 

 modifications and compounds. Especial attention is 

 given to ozone, which he tells us, upon the authority of 

 Dr. A. R. Leeds, has httle action upon the colours of 

 flowers and to hydrogen peroxide. He lays the greater 

 emphasis upon the latter compound as it is generated by 

 oil-producing plants, and thus fulfils an important 

 sanitary function. He then passes over to a considera- 

 tion of the air, respiration, and ventilation. Here we 

 find a curious error, clerical or typographical. It is 

 said that "A cubic foot of air weighs at 60"?. and 30- 

 metres Bar. 536'96 grains." The writer evidently meant 

 to say "30 inches." 



On the subject of water-supply we meet with an argu- 

 ment which we cannot accept. Says the author : — " The- 

 mineral (inorganic) constituents, however, are otherwise 

 unobjectionable in drinking water ; it is only the organic 

 matter that may render the water unfit for potable pur- 

 poses. A general support is given to this statement by 

 the well-known fact that so-called 'mineral' waters are 

 taken on account of their reputed medicinal value, which 

 is due to the salts that are present in large quantities." 



Very true, but a substance which may be taken with 

 advantage in pecuhar states of the body, and under 

 medical advice, is not on that account fit for general use 

 by persons in health. Not to speak of lead which some- 

 times finds its way into drinking-waters, salts of magnesia 

 are often present in unsafe proportions. 



Mr. Kingzett does not accept the somewhat exaggerated 

 view of the late Rivers' Pollution Commission, that 

 " Rivers which have received sewage, even if that sewage 

 has been purified before its discharge, are not safe sources 

 of drinking-water." He adduces good evidence to show 

 that sewage is actually destro}'ed in rivers. Of course, 

 if the proportion of the impurities is excessive, and if, as 

 in the streams of Lancashire, the West Riding, and the 

 Glasgow district, fresh contributions of pollution are 

 introduced every half-mile, the water must remain foul. 

 But for the further discussion of this interesting question,, 

 we must refer our readers to the original work. 



The process by which it was hoped to deal with the 

 London sewage, viz., storing it up during the flow of the 

 tide in large reservoirs, and letting it out during the ebb, 

 is condemned in very plain language. A similar judg- 

 ment is pronounced upon the recent " deodorising " ex- 

 periments of the Metropolitan Board of Works. The 

 author considers, very rightly, that " The sewage of 

 London not merely demands chemical treatment, but 

 the clear effluent alone should be discharged into the sea 

 at Barking and Crossness." 



The project for conveying the sewage entirely to the 



