46 ON THE LOSS OF HEAT 



I am not in possession of the results of any experiments, if 

 such have ever been made, to determine the ratio of friction 

 experienced by air, when compared with water, in their pas- 

 sage through pipes, under the same pressure. That air does, 

 however, experience a diminution in its velocity from this 

 cause, will not, it is supposed, be doubted, and this must affect, 

 very materially, the current of air through pipes and chimneys. 

 In practical hydraulics, it is well known, that, without alter- 

 ing the column of pressure, the quantity of water discharged is 

 greatly diminished, by merely lengthening the conduit-pipe. 

 " Comparing the experiments on the flow of water through 

 conduit-pipes, as recited in Bossuet's Hydrodynamiquc, I find, 

 after making the proper reductions, that the velocity o f p ro- 

 jection from the bottom of a cistern, is diminished about five 

 times in the passage through an horizontal tube of one inch in 

 diameter, and fifteen feet long. Consequently, while one part 

 of the actuating force is discharged from the orifice, twenty- 

 four parts are consumed in gliding against the sides of the pipe. 

 Every particle contained must hence have repeated its contact 

 no less than twenty-four times, before it made its escape ; that 

 is, the whole column of fluid must have inverted its internal 

 arrangement at each interval of l\ inches."* 



The principal article of fuel used in the United States, is 

 forest wood, which, from necessity, or choice, will continue to 

 be so in many sections of the country, notwithstanding the 

 abundant supply of anthracite and bituminous coals already 

 discovered in some of the States. 



The difficulty of consuming small quantities of anthracite 

 coal in open grates, must operate to prevent its general intro- 

 duction into use, unless this difficulty can be removed; any 

 suggestions, therefore, which may possibly tend to lessen this 

 objection to an article of such vast importance to the commu- 

 nity, will not be considered irrelevant to my subject. 



It is very well known, that no particular difficulty is ex- 

 perienced, under ordinary circumstances, in consuming small 



»Mr. Leslie on Hea' 



