236 On Warming and Ventilating 



meats of this kind, that the plan has failed in many instances. 

 And such will ever be the case with the best inventions, in 

 the hands of men who are unacquainted with the principles on 

 which they are founded. 



Nothing can be more obvious, than the decided advantage 

 which this stove possesses over all others, and nothing re- 

 mained for its improvement but to give its different parts their 

 proper proportions, and to vary its construction, so as to admit 

 of its easy management in domestic use. By the former im- 

 provement, a larger quantity of air is admitted in proportion 

 to the fuel consumed, and of course at a lower temperature. 

 The advantages which result from this improvement will be ob- 

 vious. The ventilation of the rooms warmed by it, is much 

 more complete from a greater quantity of air being admitted ; 

 the temperature is more uniform, from the air being more dis- 

 persed; and, lastly, from the air being heated by a greater 

 surface at a lower temperature, the apparatus is not in the least 

 degree injured by the fire, and hence there does not appear to 

 be any limit to its durability- 

 Nothing can be more vague and uncertain, than the opinions 

 which have been formed of the different apparatus used for 

 warming rooms by heated air. It has in consequence appeared 

 to me a desideratum in inquiries of this nature, to be able to 

 ascertain the power and merits of a stove, as we do those of an 

 engine. For this purpose, my first object was to get an in- 

 strument capable of measuring the velocity of currents. After 

 trying a variety of methods, I have found one with which I am 

 perfectly satisfied. It consists of a very light brass wheel, in 

 the form of that for the first motion of a smoke-jack. An end- 

 less screw upon the same axis gives motion to a wheel of fifty 

 teeth, on the axis of which is an index, which is watched by 

 the eye, when the instrument is exposed to the current. The 

 wheel acted on by the current, is about two and a half 

 inches in diameter, and the vanes or sails are eight in number, 

 and fill up the whole circle, when their faces are parallel to 

 the plane of their motion, and they are adjusted to an angle of 

 45*. Under these circumstances, I have found that fifty re- 



