576 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



than it does in looking at the ground-glass globes 

 of single gas-burners. On one of the walls of the 

 illuminated hall was a series of silk specimens 

 of all colors and tints, some of the shades being 

 very delicate. Near by was the notice,- "The 

 electric light does not alter colors." This state- 

 ment seemed to be verified by the experiments. 

 At any rate, the smallest differences of tints' were 

 easily distinguished. After a time the g#s was 

 relighted, but, notwithstanding its great brilliancy 

 at first, its light now seemed quite feeble, and of a 

 dirty-yellow color, as compared with the electric 

 illumination. 



The cost of electrical illumination is estimated 

 at from one-half to one-third the price of gas, 

 for equal quantities of light. 



The anti-malarial action of the eucalyptus- 

 tree is called in question by Mr. Arthur Nichols, 

 who, writing in Nature, says that in Queensland, 

 in the very heart of a forest extending for many 

 miles in everytlirection, and composed mainly of 

 eucalyptus of; every variety, he has himself suf- 

 fered from mfilaria, and has known many instances 

 of febrile attacks among shepherds and stock- 

 men in the locality. On inquiry, he learned that 

 these attacks were not confined to any particular 

 year, but that every year some cases might be 

 expected. Again, it has been asserted that, wher- 

 ever the eucalyptus had been introduced on a 

 considerable scale in Algeria, the mosquitoes all 

 disappeared. But this correspondent, writing of 

 Australia, says that he has found these pests so 

 intolerable on high land, where almost the only 

 variety of tree to be found was one variety or an- 

 other of eucalyptus, and sometimes all, that sleep 

 was impossible while camping out at night, life a 

 burden during the day, by reason of these insects. 



The anti-malarial properties of the Eucalyp- 

 tus globulus are commonly supposed to depend 

 exclusively on the emanations from the leaves ; 

 but Mr. A. W. Bennett thinks it most probable 

 that the chief effect is produced by the action of 

 the roots on the soil. Writing of this subject in 

 Nature, he remarks that the effect of the planting 

 of forests in increasing the rainfall is often er- 

 roneously reputed to be due to the " attractive 

 force of the trees" on the moisture in the air, 

 similar to that exerted by a range of mountains ; 

 but this supposition he regards as untenable. 

 The mode in which trees mainly act is, he says, 

 by their roots arresting the rainfall which would 

 otherwise escape by the natural drainage of the 

 country ; the combined forces of capillarity, os- 

 mose, and transpiration, then cause the ascent 

 through the tissues of the tree of the water thus 



arrested, and the larger portion is eventually 

 given off into the air through the stomata of 

 the leaves. In t^ds way a forest-tree will in a 

 very short time give off into the air its own weight 

 of water, which is again deposited as rain or dew. 

 It is quite possible, however, that the effect of the 

 planting of trees may be apparently the reverse 

 of this in swampy regions without natural drain- 

 age. The water then accumulates in the soil ; 

 and if the country is bare of timber-trees and the 

 sun powerful, a rapid decomposition takes place 

 of the herbaceous vegetation, with consequent 

 emanation of malarial vapors. If trees be plant- 

 ed, the effect is to supply natural drainage ; the 

 accumulation of water in the soil, and the conse- 

 quent noxious effluvia, will be diminished and 

 finally prevented, and the atmosphere rendered, 

 if not drier, at least more wholesome. 



Needed Inventions. — Under the title of " Room 

 for Invention," the Polytechnic Review points out 

 a number of mechanical problems, the solution 

 of which would be of inestimable service to the 

 human race. The writer of the article, while ac- 

 knowledging the great benefit conferred by the 

 invention of reaping and mowing machines, calls 

 attention to the need which exists of machines 

 for gathering root-crops and fruit. Sundry fibres 

 that ought to be available in textile art, as ramie, 

 are still intractable. The gorgeous aniline colors 

 fade with a summer's sun. Household fires — 

 once the very emblems of health and cheerful- 

 ness — now poison us insidiously but surely. " Our 

 sewers and drains," the author goes on to say, 

 " are confounded in name and use, and both of 

 them are poisonous. Our chimneys breathe forth 

 smoke which is unconsumed fuel, and hence waste- 

 ful. Our steam-boilers, with partly-consumed fuel, 

 supply our engines with wet steam, and the en- 

 gines (whose cylinders have to be supplied with 

 oil, through faulty design and workmanship) 

 waste part of the remainder. Our horses, shod 

 with no regard to humanity or for tractive effect, 

 draw wagons or cars which rattle our teeth out, 

 on roads or rails which rattle the vehicle to pieces. 

 The explosives which long ago were constrained to 

 throw hurtful missiles for miles, have but in one 

 instance — blasting — been employed in peaceful 

 work ; if we may except the gunpowder pile- 

 driver, the precursor of a long line of explosive 

 motors yet to come. There is yet no ice-machine 

 which will satisfactorily and economically com- 

 pete with Nature in supplying a commodity now 

 so great a necessity. For these and hundreds 

 of other evils, inventive genius must provide the-- 

 remedy." 



