886 Traxsactions of the American Institute. 



ing the equation. 4. Hunger affects the vahic of the personal equa- 

 tion. 5. That the mental state of the observer has some influence 

 on the personal equation. Mr, Rogers also gives a summary of his 

 investigations to determine whether changes in the size, shape, or 

 illumination of the object affect the power of the observer; in con- 

 clusion, he states that the results he found do not settle definitely 

 any point except the general variability of the personal equation. 

 "We may, therefore, make the general statement that the velocity of 

 thought in the same individual is not uniform, and that while we 

 know that one will think slow or fast, it is still impossible to deter- 

 mine the causes which produce these changes in the speed of thought. 



An item, read by the Chairman, relating to consuming smoke in 

 furnaces elicited considerable discussion. 



Mr. T. R. Pickering said that a smoke-consuming furnace was 

 tried at the Dry Dock Iron Works in this city. It was Mr. Under- 

 hill's plan. Some years ago he had seen a single boiler forty inches 

 in diameter, two feet long, with twenty square feet of grate surface 

 at a level of only thirteen inches below the bottom of the boiler. 

 The people of the neighborhood and the owners, were much annoyed 

 by the large amount of smoke resulting from the imperfect combus- 

 tion of the fuel. So anotlier boiler of the same size was placed by 

 the side of the other ; the last boiler had a grate surface of twenty- 

 five square feet, about five feet more than the other, but the grate 

 surface was placed at a level of thirty-two inches below the bottom 

 of the boiler, by which the space allowed for combustion was much 

 increased; and as a consequence, the smoke nuisance was avoided, 

 and a great economy in fuel was effected. 



Prof Phin remarked that the plan alluded to by the Chairman in his 

 summary of news, was ineflicient for the purpose, as the gaseous 

 products of combustion carried back into the furnace would dilute 

 the air and reduce combustion. And as the process becomes more 

 perfect, the impurity of the air for combustion would increase until 

 a point might be reached at which the tire would be extinguished. 

 The great waste of combustible matter that passes off' through the 

 chimney is not carbon, but carbonic oxyd. 



Mr. G. IT. Babcock stated that an inventor from one of the west- 

 ern States came to Providence, Rhode Island, some ten years ago, 

 and fitted an apparatus somewhat like the one here mentioned to the 

 boilers of the Roger AYilliams Manufacturing Company. lie applied 

 a blower to take the smoke from the chimney and return it beneath 



