NOTKS ON STATIONAEY ENGINES. 47 



time so far familiar with coi'tain long-stroke engines as to 

 be able to say at a dista.nco of a quarter of a mile whether 

 the correct or usual speed was being worked ; this would 

 obviously be impossible if high speed was adopted and 

 correspondingly short strokes. Tliis I'aises the question 

 ao'ain as to what must be considered as high speed, and it 

 may be remarked that a piston speed of 1,000 foot was 

 thought of, with sti'oke of from three feet down to eighteen 

 or twenty inches. One or two speakers seem to have had a 

 greater number of revolutions in view ; for instance, when 

 refei^enoe was made to the Corliss gear proving unsuitable 

 for such speeds, or by three cranks, whether triple or com- 

 l)ound. 



Several single-acting engines, with three or more cylin- 

 ders, are in use, but two, as referred to by Dr. Ryan, would 

 not bo so oflicient. 



The bump referred to by Mr. Spencer, at the bottom of 

 stroke of vertical inverted engines, will pi'()ba,bly be largely 

 got over by higher speed, or by three cranks, whether triple 

 or compound. 



The wheel draught referred to by Mr. Newall is instructive, 

 but all the same ho will excuse the preference expressed in 

 the paper. Perhaps Mr. Spencer will ono day favour us 

 with an account of the system of boiler-sotting referred to 

 by Mr. Newall. The writer remembers a case many years 

 ao-o .showing the objectionable corrosion, which is usually 

 charged against them, but how far this is explained by the 

 old-fashioned use of common bricks and lime mortar, it is 

 now impossible to say. 



