366 Mr. Langton on Artificial Climates. 



Tredgold, is admirably calculated for showing the principle 

 to be borne in mind in contriving the manner of connecting it 

 together. The vast length, however, of the sum of each series 

 of ribs, and the considerable variations of bulk to which iron 

 is subject from changes of temperature, would present most 

 formidable difficulties in endeavouring to obtain stability with 

 long connected lines of that material, particularly if those con- 

 nections must be confined at each end ; there would be re- 

 quired not only such minute accuracy as to dimensions, but 

 also such exquisite nicety in rendering all corresponding parts 

 exactly the same in point of flexibility and elastic power, for 

 securing the whole from general derangement of stability by 

 any partial excess of strength, that such a task would be hope- 

 less in theory, and extremely doubtful as to its result in prac- 

 tice. 



The best arrangement would appear to be to connect firm- 

 ly all the tops of the columns with each other, and with the 

 party walls of the houses, by timbers something similar in 

 form to the yards of ships; their transverse sections should 

 be elliptical in about the proportion of fourteen inches to thir- 

 teen, and their greatest diameter placed horizontally ; stiffness 

 might be thus most effectually and ceconomically gained, as 

 the bearings of such beams would be divided by suspension 

 from the roof, and their own weight would prevent them from 

 curving upwards when acted upon by a compressing strain ; 

 their suspension should be adjusted horizontal when the tem- 

 perature was at a mean elevation. Upon the tops of columns 

 thus firmly retained in their places, there would be no more 

 difficulty in placing a number of detached roofs of iron or 

 other material, additional labour and scaffolding excepted, 

 than there would be in placing such roofs on the ground be- 

 neath. The glass roofs would range on a level with those of 

 the houses, except that it might be desirable to have an addi- 

 tional story on the north side, to prevent the warmed strata of 

 air being quite so rapidly carried away from the surface of 

 the glass in the coldest weather. Each division of roof would 

 be about thirty-three feet six inches square, and in form would 

 be two roofs intersecting each other at right angles, thus giv- 

 ing to each house an avenue to the one opposite. For the 

 skeleton framing of each division of roof, cast-iron, jointed at 

 the ridges and points of intersection, might be appropriated 

 in exceedingly elegant forms, with the unusually concurrent 

 advantages of durability and cheapness. The glazed frames 

 might be either of iron or wood ; the former material would 

 admit of their being so made as least to obstruct the light, and 

 is the most durable; wood, however, possesses a great advan- 

 tage 



