Mr. Langton on Artificial Climates. 365 



the place by blending the works of nature in their rarest and 

 most beautiful forms with those of art when devoted to that 

 purest and noblest of all worldly purposes, — the alleviation of 

 human suffering, would occasion a necessity for keeping the 

 ventilation of the houses wholly distinct from that of the area 

 or garden, that no air which had been deprived of any por- 

 tion of its salubrious properties, either from the action of ve- 

 getable life, or the decomposition of dead vegetable matter, 

 should be inhaled, except when the enjoyment of exercise 

 would render such a circumstance unavoidable, and when the 

 doing so, to an extent not necessarily otherwise than infinitely 

 trifling, could hardly even in theory be deemed disadvanta- 

 geous. In roofing over this inclosed space, such materials 

 should be used as admit of offering the least obstructions to 

 light and ventilation ; airiness of effect should be gained with- 

 out sacrificing strength, and cheapness without decreasing 

 durability : these conditions obviously suggest iron as a fit 

 material to be largely employed, especially for all columnar 

 supports, as being cast hollow they would also serve as 

 spouts for conveying down the rain-water; and their slight 

 variations of length from alternations of temperature, instead 

 of being a disadvantage, might on the contrary be used as a 

 self-acting means of regulating the quantity of ventilation, by 

 having many of the glazed frames swing on their centres, and 

 firmly connecting the short arms of levers attached to them 

 with the bases of the columns by long rods of wood or other 

 material not subject to practical variations of length by mode- 

 rate changes of temperature : the difference of length thus ob- 

 tained in the present case would be about one hundredth of an 

 inch for every three degrees by Fahrenheit's thermometer, a 

 maximum of height is obtained by this material with a mini- 

 mum of diameter. As regards lateral connections for the pur- 

 pose of giving sufficient stability to the roof to resist winds, it 

 would be desirable to form them either of timbers fixed hori- 

 zontally in right lines and crossing each other at right angles, 

 the extreme ends abutting against the party walls of each 

 house, or of iron ribs so curved as to admit of their acting 

 like springs, in so adjusting themselves by extension or con- 

 traction that the distances between their ends should not vary 

 with the temperature. Iron thus employed would unques- 

 tionably admit of more elegant forms in detail than any other 

 material to be procured at any reasonable cost ; and in such a 

 construction what would be most beautiful in detail would be 

 the most likely to produce the best effect as a whole. If iron 

 was the material exclusively adopted, the roof of a glass-house 

 in Messrs. Pellat's establishment, designed by the late Mr. 



Treclgold, 



