486 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



combustible, one burning in sunshine will consume more rapidly 

 than one burning in darkness. 



Fourth. That combustion during the winter is more vigorous than 

 in summer, because a given volume of air contains more oxygen, 

 is denser and dryer. 



Fifth. That slight currents by causing a flame to flare and come 

 in contact with more air in a given time, causes more rapid com- 

 bustion, and by presenting greater surface from which radiant 

 heat issues to warm the combustible about to be burned, increases 

 the rate of combustion. 



Sixth. That the diminished draft of chimneys in very hot weather 

 when the general atmosphere is at rest, and the sunshine intense, 

 is due to upward currents on the outside of the house, arising from 

 the heated surfaces of the roof and walls, which currents by fric- 

 tion draw outward through cracks and open doors and windows 

 the air from the interior of the house, and so lessen the pressure 

 within and overcome the draft of the chimney. 



Seventh. That the popular impression that intense sunshine 

 lessens the draft of chimneys, is founded in fact. 



The first regular business before the Polytechnic was the exami- 

 nation of new inventions and discoveries. 



New Earth-Pulverizek. 



This machine, the invention of Messrs. Fithian Young, was 

 exhibited in model. It consists of a series of rotary cutters so 

 shaped and combined as to act on the soil in a nearly uniform 

 manner, while the whole machine has a forward movement. Mo- 

 tion is communicated to the cutters by a large wheel having on its 

 periphery a double row of slats forming a very obtuse angle at 

 their points of contact, the eflTect of which is to take a firm hold 

 of the earth whatever may be its condition. The whole is mounted 

 on four wheels, which are brought into use only when it is being 

 moved to and from the field. 



As this is a new attempt to solve a question of the greatest 

 importance — the proper method for preparing the ground for 

 seed — the machine was subjected to the closest scrutiny of several 

 mechanicians present. Its construction was admitted to be inge- 

 nious, but its practical value can only be determined by repeated 

 tests. Fields of the same dimensions and prepared for the same 

 kind of seed by the plow and hai-row, and by this new machine, 

 would by their yield show precisely the advantages secured by 



