ifl, B. (^uinby on high and loio pressure Boilers. 313 



Art. XIV. — On, high and low pressure Boilers. 

 By A. B. QuixBY. 



The following is the substance of a paper communicated 

 by the author to the committee appointed by the Literary 

 and Philosophical Society of the City of New- York, to in- 

 vestigate the causes which gave rise to the explosion of the 

 boiler on board the Steam-Boat -Sltna.* 



To determine the comparative eligibility of the high and 

 the io2o pressure steam-engine, the two following things ap- 

 pear to me necessary to be considered.- First, the liability 

 of each engine to explode ; and secondly, the danger, or 

 injury, which each engine is capable of producing in case aii 

 explosion takes place. 



To determine the comparative liability of the two engines 

 to explode, it will be necessary to consider the four following 

 things : — the diameters of the boilers used in thetvvo engines ; 

 the elastic force of the steam in each boiler ; the tenacity of 

 theinetal of which the boilers are composed ; and the thick- 

 ness of each boiler. 



The diameter of the boiler on board the Mtna. was thirty 

 inches ;^ and the diameter of a boiler for a low pressure 

 engine of 'equal power would be about ninety inches ; or 

 three times as great. 



The elastic force of steam in the boiler of the Mtnsi was 

 usually 150 lbs. per square inch; and the elastic force of 

 steam in a low pressure boiler is usually 10 lbs. per square 

 inch. 



The tenacity of the metal of which boilers ai-e composed 

 is about 60,000 lbs. ;• or six-sevenths that of good wrought 

 iron.t 



As, however, the cylinder which constitutes the boiler 

 is not solid metal, But is composed of plates riveted together, 

 it will be necessary to diminish the number which expresses 

 the tenacity. 



Let', therefore, the tenacity be put at 30,000 lbs. in place 

 of 66;000. 



* The communication was made at the request of Dr. Dekay, chair- 

 man of the committee. 



t The tenacity of any metal is usually expressed the by greatest weighb 

 in lbs. which a bar one inch square, of that metal, is capable of sustain- 

 ing when pulled endwise. 



Vol. IX. No= 2. 40 



