320 .d. B. i:^iiinhii on Crank Motion. 



which this difference (if indeed it exists,) may be much niote 

 obviously and properly referred. 



On the subject of the application of the rotative motion by 

 the crank, it is now known, and mathematically established, 

 that it occasions "no loss whatever of the acting power;" and 

 with respect to the smallness of the engines, it is obviously a 

 circumstance insufficient to produce the difference stated. 

 There must therefore be other causes on which this differ- 

 ence depends. But what other causes, it will be asked, can 

 be sufficient to produce the prodigious difference of three.- 

 fourihs^ in the performance of two similar engines ? The an- 

 swer is plain. It is, first, the injudicious or wasteful applica- 

 tion of the coal consumed ; and, secondly, the want of a con- 

 stant and sufficient load in the buckets, during the time the 

 engine is in action. The latter, it is believed, is the chief 

 cause on which the difference depends. 



There is now one other thing to be noticed before I pro- 

 ceed further in my examination of this reply from the writer 

 of the article in the North American Review. 



In Rees' Cyclopaedia, and likewise in the North American 

 Review, each writer makes the quantity of coal consumed to 

 be the measure of the power of the respective engines^ 

 But does not every person know, who is in the least degree 

 acquainted with the steam-engine, and with the science of 

 Mechanics, that the quantity of coal consumed is not the 

 measure of the power of a steam-engine? 



1 now proceed in examining the reply from the writer in 

 the North American Review. "Before Mr. Quinby con- 

 cluded," says this writer, "that a very great blunder was 

 made in the^e estimate?, it would have been well for him to 

 Iiave hunted up some information on the subject.'' 



Inanswer to this remark, it is now stated, that the more in- 

 formation Mr. Quinby has hunted up on the subject, the more 

 he is confirmed in his original belief that " a very great blun- 

 der wal committed by those who made the estimates." 



It has already been shown that one of the causes to which 

 the difference is attributed does not exist; and the other, it is 



that he must also have believed that the application of the rotative mo- 

 tion by the crank occasions a loss of at least one-third of the whole 

 power. And this opinion had, no doubt, its full weight with the writer' 

 of the article in the North American Revieiv. 



