l8o3' On Thrashing Machines, 50 j 



Wliich, upon the supposition that eight bolls are tlirash- 

 eJ per day, as stated by your correspondent, amounts to one 

 shilling and fivepencc per boll. Now, as corn can be thrashed 

 by the flail at less than one shilling per boll on an average, the 

 loss attendant upon small machines does not require furthei: 

 demonstration. 



I may here add, that from an attentive examination of ma- 

 ny tlirashing instruments of different powers, 1 am satisfied 

 that a boll per hour for every horse employed, is a fair ave- 

 rage calculation of the quantity of grain thrashed by these ma- 

 chines. No doubt but tliat, in particular seasons, with short 

 straw and fine grain, a greater quantity Vv'iil be beat out, but 

 still, as a general principle, the above ma}^ be held as nearly 

 eqtial to the ordinary produce. I have seen fifteen bolls th rain- 

 ed in one hour with six horses, but always found a great de- 

 duction must be made when a regular journey is taken, inde- 

 pendent of the V7aste of time which unavoidably happens. In 

 some seasons, also, the siraw is so long, and the grain so un- 

 productive, that few people, who are in the habit of managing 

 these machines, will call in question the propriety of assum- 

 ing a boll per hour for every horse employed as a fair result 

 of thrashing machine labour ; I am rather afraid, that some 

 will consider it as exagr;erated. 



I have hitlierto argued the question, as if small machines 

 were capable of separating the grain from the straw in a suf- 

 ficient way. As this however is a matter of dispute, and con- 

 cerning which I am not altogether satisfied, allow me to state 

 my sentiments in a cursory way, and to express a wish that 

 some of your correspondents, practically concerned in the v/ork- 

 ing of such machines, would correct me w^hen I am wrong, and 

 eincidate the subject with more perspicuity. 



In my last letter it was stated, that a velocity not less than 

 two thousand feet per minute of the circumference of the 

 drum, or cylinder, was required to ensure perfect thrashing, 

 and that the best machines even exceeded that pitch consider- 

 ably : Now it strikes me, that a small macliine is uncapable of 

 sustaining such velocity, at least those I have inspected were 

 neither wrought at that rate, nor were they calculated for il;^ 

 in any single point. To give velocity to a machine slenderly 

 coastructed is almost physically impracticable ; at least, if 

 given, the machine is exposed to utter destruction, a circum- 

 stance deserving much attention in the construction of every 

 machine, whatever be its size. 



According to the ideas which occur to me upon the subject, 

 two things deserve attention in the construction of small ma- 

 chines, in order to render them, if not profitable implements, 

 U u u 3 Jit 



