SCIENCE IN SHORT CHAPTERS. 



stone by this acidified water. This, of course, is very weak acid in- 

 deed. That which I used for testing the stone was many thousand 

 times stronger, but then I exposed the stone for only a few days in- 

 stead of many thousand days. 



As above stated, my experiments were but rude, but I think it 

 would be quite worth while to construct crushing apparatus capable 

 of registering accurately the pressure used, and to operate with stand- 

 ard solutions of acid upon carefully squared blocks of standard size, 

 and thus to make comparative tests of various samples of stone when 

 competitions for building materials are offered. In the case of the 

 Birmingham and Midland Institute building there was no such com- 



Eetition ; the choice was left entirely to the architect, and my exaui- 

 lation was unofficially conducted upon the material already chosen 

 with the intent of protesting if it failed. As it stood the test I 

 merely reported the results informally to the architect, the late Sir 

 Edward Barry, no further action being demanded. 



CHAPTEE XLII. 



HOME GAKDENS FOE SMOKY TOWNS. 



THE poetical philanthropists of the shepherd and shepherdess 

 school, if any still remain, may find abundant material for their dole- 

 ful denunciations of modern civilization on journeying among the 

 house-tops by any of our over-ground metropolitan and suburban 

 railways, and contemplating therefrom the panorama presented by a 

 rapid succession of London back-yards. The sandy Sahara and the 

 saline deserts of Central Asia are bright and breezy, rural and cheer- 

 ful, compared with these foul, soot- smeared, lumber-strewn areas of 

 desolation. 



The object of this paper is to propose a remedy for these metropol- 

 itan measle-spots, by converting them into gardens that shall afford 

 both pleasure and profit to all concerned. 



A very obvious mode of doing this would be to cover them with 

 glass, and thus convert them into winter gardens or conservatories. 

 The cost of this at once places it beyond practical reach ; but even if 

 the cost were disregarded, as it might be in some instances, such 

 covering in would not be permissible on sanitary grounds ; for, dole- 

 I ful and dreary as they are, the back-yards of London perform one 

 ^ry important and necessary function ; they act as ventilation-shafts 

 between the house-backs of the more densely populated neighborhoods. 



At one time I thought of proposing the establishment of horticult- 

 ural home-missions for promoting the dissemination of flower-pot 

 shrubs in the metropolis, and of showing how much the atmosphere 

 of London would be improved if every London family had one little 

 sweetbrier.bush, a lavender plant, or a hardy heliotrope to each of its 

 members ; so that a couple of million of such ozone generators should 

 breathe their sweetness into the dank and dead atmosphere of the 

 denser central regions of London. 



A little practical experience of the difficulty of growing a clean cab- 

 bage, or maintaining alive any sort of shrub in the midst of our soot- 



