EXPERIMENTS WITH AIR FURNACES. 



TOURING the past winter we devoted consider- 

 able time to the investigation of the mechanism 

 and operation of air furnaces, with the view of as- 

 certaining by practical experiment the nature of the 

 defects so generally complained of; and we also 

 entertained the design of attempting to remedy 

 these defects. What are known as " portable fur- 

 naces " are now largely used in all houses of mod- 

 erate dimensions, and as these in no respect differ 

 in construction from the kinds placed in brick 

 chambers in large houses, attention was given to 

 this form of apparatus. After a full examination 

 of the various popular devices offered by manufac- 

 turers, two were selected as embracing the most 

 sensible and desirable features in form and con- 

 struction, and these were subjected to practical 

 trial. It should be observed .that all the various 

 patented contrivances found in the market are in 

 many particulars essentially alike. The " im- 

 proved " kinds, or those quite recently invented, 

 appear to be more objectionable in construction 

 than others which have been longer known. In 

 the newer devices, the inventors seem to think that 



