174 PORTABLE STEAM-ENGINE; 



Advantage of ( Sand has not hitherto been ufed in blading at the flate quar- 

 ^ S ro C ck. rSeSinries in Kirkb y I rel eth. The matters do not think it would 

 fucceed well in their work. I have frequently Teen Mr. Fifher 

 ufe it in limeflone rock near this town : He fays it anfwers the 

 befl in deep holes, but thinks that fand is more liable to be 

 blown out than (lemming. He alfo confiders it as the mofl 

 advantageous method of working, in driving levels, and blad- 

 ing in firm rock, to ufe ftrong charges of powder, that the 

 Hone may be fufficiently broken by the explofion to be re- 

 moved without much affiftance from the hammer, the pick, 

 or the lever : For thus the expedition of the work amply com- 

 penfates for the fmall addition which is requifite to a common 

 charge of powder. 



I am, Sir, 



Your's refpeclfully, 



WILLIAM CLOSE. 



IV. 



Defer iption of a portable Steam-engine, invented by Mr. Samuel 

 Clegg*, David Street, Manchejier. Communicated by 

 Mr. Dalton, Lecturer at the Royal Injlitution, fyc. 



Defcription of a 'A HIS engine is worked by four copper valves in the ufual 

 £«anjrcngi!ie. manner, but the mechanifm for lifting them is very different 

 from any hitherto made : there are no levers employed for 

 opening the valves, and there is no hand gear. The fleam 

 and exhauflion valves are on the fame horizontal plane ; thofe 

 which are vertical to each other are not like thofe hitherto 

 ufed, both expofed to the fleam or both to a vacuum ; but by 

 a iimple contrivance in the conflru&ion of the nozzles, the 

 one is expofed to the fleam while the other has a communica- 

 tion with the condenfing vefTel. From what has been faid it 

 may eafily be perceived, if the two valves be connected to- 

 gether by a ftraight rod, that when this rod is lifted, 1 the pref- 

 fure is given to the piflon, and the machine is put into mo- 

 tion ; and if the other two valves be connected in the fame 



* Late apprentice to Meffrs, Boulton and Watts, of Birming- 

 ham. 



manner 



