On the means of safety in Steam Boats. 



38.52 

 43.20 



48.06 



According to Mr. Renwick, 

 4 atmospheres, . . 291° 



8 " .... 331 ... . difference, ... 40. 

 and so usually stated. 



Besides, the necessity or expediency of anticipating the danger is 

 made more striking by the law of resistance to the passage and es- 

 cape of steam through openings, as its velocity does not increase in 

 the ratio of its elasticity. The Treatise of Prof. Renwick, (p. 87,) 

 assigns it the following ratio, viz. 



At 1:1 atmospheres, 873 feet per second. 



2 " 1405 " " 



4 " 1663 " " 



6 " 1785 " " 



8 "....... 1852 " " 



Wherefore, I conceive the best means of safety is, in this as in other in- 

 stances of liability tDf exposure to an uncontrollable explosive force, to 

 anticipate the cause m\Aqjrevent\\.s sudden accumulation or occurrence. 



To this end, as the undue decline of the water is the proximate 

 cause, I make that decline of it operate as a power to give the alarm, 

 or notice of the near approach of danger. 



The method of safe-guard to be described cannot indeed prevent 

 the 'primitive cause, whether it be neglect, defect or leakage ; but, it 

 will audibly announce when either of these causes has diminished the 

 water to the hmits of safety, and the borders of danger. It will make 

 it known not only to the engineer, but to others, seasonably, to provide 

 against the tremendous consequences of disregarding the warning. 



With this view 1 make a float of heavy plank, the specific gravity 

 of which is about .900; or, preferably, of metallic plate or lead, 

 )nade just buoyant by attaching cork securely to it, so that when 

 raised out of the water in some degree, it will operate as a weight, 

 or power upon the short end of a lever, with which it is connected 



