ON THE MERITS OF IRON AND WOOD FOR ROOFS. 



79 



the application of labour. Entering, therefore, on this all-impor- 

 tant subject, I shall confine my observations in the first place to 

 advantages of hot water over steam, which are, m my opinion, 

 very great, particularly where coals are expensive ; for, to 

 generate steam an enormous consumption of coals, or oven 

 coke, which is nearly as expensive, is indispensably required 

 as a weaker fuel will be found of no avail. This is the first evil 

 of the steam system, and the second is, that a man s time must 

 be nearly, if not wholly employed in affording that constant at- 

 tention which is necessary to keep up the fire. Then in the third 

 place, there is a considerable loss not only of time, but ot tuel 

 also before the pipes become filled with steam. This is a very 

 important part to which, perhaps, due attention has not been 

 paid, for it may not be generally known that steam travels through 

 the pipe in a time no shorter than it requires to make them nearly 

 as hot as itself; for steam, the instant that it comes in contact 

 with a body colder than itself becomes condensed, audits onward 

 motion is of course impeded. Again, the moment the fire be- 

 comes too weak to keep the water at the boiling point, so that 

 steam may be generated, it immediately ceases to furnish heat to 

 the pipes; consequently the pipes soon become cold, and this 

 is the fourth evil of heating by steam, which is avoided by the 

 use of hot water ; for the instant the fire is ignited and the water- 

 gets warm, the particles of the fluid are set in motion, and circu- 

 lation in the pipes commences, and continues until the whole of 

 the fuel is consumed, or so long as there remains any heat in the 

 furnace, in the bricks, or in the boiler. Still further, I have 

 found two pipes each four inches in diameter when filled, the 

 one with water at a heat of 200 degrees, and the other with 

 steam, the one with the hot water would contain a much greater 

 and more enduring body of heat than one filled with steam; 

 and I have no doubt that if, when both pipes are heated up to the 

 stated temperature, the fires were suffered to expire, the pipe 

 containing steam would cool as much in one hour as the hot water 

 pipe would in six or seven hours. These facts are stated from 

 accurate observation, frequently repeated, and from exact calcu- 

 lations, very severely tested; they may, therefore, be considered 

 to demonstrate in the last place, the decided advantages which the 

 plan of heating by the circumvolution of hot water passes over 

 the rival system of heating by the diffusion of vapor. To the 

 superiority of the hot water plan, as to economy, both of fuel and 



