488 Thompson's Practical Treatise oti the Construction 



iron roof on a hot day." This may be perfectly true, without 

 its following, as a general conclusion, that all iron roofs are bad. 

 There can be no doubt whatever that iron sashes, tightly fitted 

 in between iron rafters, will be extremely difficult to move in hot 

 weather, and the act of moving them will be in great danger of 

 breaking the glass ; but may not this be avoided, by not fitting 

 them in so tightly between the rafters, or, as Mr. Thompson 

 elsewhere (p. 21.) recommends, " having the sides of the lights 

 made of wood, with small rollers affixed to the under side, to 

 make them run easy?" In some remarks on this subject in our 

 preceding Number (p. 446.), we have recommended that, where 

 sash-frames are formed of iron, either wholly or in part, they 

 ought invariably to be small, on account of the difficulty of moving 

 them, and the consequent danger of breaking the glass while so 

 doing. For this reason, we would never employ iron sashes 

 in pits or frames at all ; and in the roofs of larger structures, we 

 would have the sashes narrow and short, with the side styles, 

 and top and bottom rails, of wood. 



It is generally supposed among gardeners, that we advocate 

 iron hot-houses ; but we never advocate anything absolutely and 

 exclusively. We would decidedly employ iron in many cases ; 

 and, in many cases, would also as decidedly employ wood. The 

 great error in the "practical men," as they call themselves, is in 

 being too exclusively in favour of either the one or the other. 

 Mr. Thompson states that Mr. M'lntosh, head gardener to the 

 King of the Belgians, and Mr. Paxton, gardener to the Duke of 

 Devonshire, think with him on the advantages of wood over 

 iron. That may be the case ; but we have a higher opinion of 

 both, than to suppose that either of them is exclusively in 

 favour of either the one mode or the other. All Mr. M'Intosh's 

 opinions against iron houses and curvilinear roofs, backed by the 

 authority of Mr. Atkinson, will be found quoted in our Fifth 

 Volume (1829), p. 185, 186, and 187. We should be sorry 

 to suppose that Mr. M'Intosh has not since seen reason to alter 

 his opinion ; at all events, we hope that, if he still retains it, he 

 is enabled to raise it on a better foundation. 



One object of the pamphlet before us is, to recommend a 

 boiler invented by Mr. Thompson, and which he calls an 

 *' economic, oval-shaped, wrought-iron boiler." This he says 

 " has not only received the direct approbation of every engineer 

 who has witnessed its operation, but is considered by them, and 

 by all who have adopted it, as the most simple and economical 

 of all the plans yet submitted to the public." We should like to 

 see a list of the engineers alluded to. This invention is anything 

 but simple, though we have no doubt it will act very well for 

 three years ; a time respecting which Mr. Thompson says, " I 

 always offer a guarantee to all who may employ me to fix it, that 



