General Notices. 565 



action of the apparatus ; but the time requisite to obtain a given temperature, 

 and the permanence of that temperature, depend on the mass of heated matter, 

 the relative times of heating and cooling being inversely as the mass divided 

 by the superficies." [The rule here given may safely be taken by gardeners 

 as a guide for green-houses, but the heating surface will require to be increased 

 a little for stoves.] 



Ventilation is next treated on by Mr. Hood. " All air respired from the 

 lungs is found to have lost a proportion of its oxygen, and to have acquired a 

 proportion of carbonic acid gas and vapour, and the quantity of air which will 

 require to be changed may be taken as 3§ cubic feet per minute for each person 

 a room contains. • The author dwells at considerable length on the phy- 

 siological effects consequent on these changes, and details several striking 

 instances of the great advantages resulting from improved ventilation, in places 

 which had previously been unhealthy. All ventilation may be placed in one 

 of two classes, the natural, or the mechanical ; in the former, the excess of 

 temperature of the air is the primum mobile of the efflux, and the rapidity of 

 the discharge may be much increased by artificially raising the temperature of 

 the discharging pipe. The ventilation by mechanical means, as by fans rotating 

 with a great velocity, may be most advantageously employed wherever me- 

 chanical power is used for other purposes ; the great efficacy of this latter 

 mode is proved most unquestionably by the experience of the manufacturing 

 districts. The former method has recently been tried on a very large scale at 

 the House of Commons; and it is calculated by Dr. Ure that thirty-eight times 

 more fuel is expended in producing the same effect by chimney draughts than 

 b}' mechanical power. It appears, however, that the natural methods of venti- 

 lation, as by the spontaneous effusion of the heated air, through openings in 

 the ceiling, is the best calculated for ordinary purposes, but in all extraordinary 

 cases, ventilation by mechanical means is the only economical and efficacious 

 method. (Athenceum, July 13. 1839.) 



The Method of heating Houses practised in Paris seems to me worthy of 

 being copied. Whatever be the weather, frosty or wet, the moment I enter 

 one of the respectable cafes or restaurants, I find myself in a genial at- 

 mosphere. If this were only after nightfall, the lights would account for it, 

 for they are brilliantly illuminated with gas ; but it is the same at midday. In 

 the very best London coffee-houses, the cheek of the fire is the favourite 

 station, and winter reigns in the rest of the room. In the cafes here, there 

 are no fires visible, but the stoves are so managed as always to maintain an 

 agreeable warmth, and no place in point of comfort is preferable to another. 

 In the hotels or lodging-houses, however, the case is the reverse. The salle 

 for breakfast and dinner is heated with a fire of wood or coke, and has its 

 torrid, temperate, and frigid zones. The bed-rooms and parlours, with their 

 cold brick floors, marble tables, and a few billets of wood on the hearth, are 

 dismal abodes for a person accustomed to large coal fires. (Scotsman, Jan. 19.) 



Such is the high price of fuel in Paris, and on every part of the Continent, 

 and such the severity of the weather during winter, that probably no house 

 can be heated to a comfortable degree without the aid of stoves ; but, even 

 with these, to insure their full effect, the construction of the open fireplaces 

 would require to be totally altered. Perhaps the cheapest and most effective 

 mode of doing this would be to place in them one of the American stoves, so 

 strongly recommended by Cobbett. This stove, which is very well known to 

 the ironmongers of London and Birmingham, and is figured and described in 

 our JEnci/clopcedia of Cottage Architecture, we would strongly recommend to 

 gardeners who have cold comfortless rooms, and who are obliged to use 

 wood or peat as fuel. — Cond. 



Prepared Fuel for Hut-house Furnaces, fyc. — In some parts of the country 

 peat is compressed for this purpose, and Lord Willoughby de Eresby has 

 recently taken out a patent for a peat-compressing machine, which will be 

 found described in the Civil Engineer for August, 1839 (vol. ii. p. 283.). In 

 others, where coal is scarce, cow-dung, loam, and small coal are mixed to- 



