6 On the means of safety in Steam Boats. 
nt. Fahr. Difference 
L atu. emp: 100° =212° for Latm. 
121.4=250.52 . 38.52—diff. between 1&2, 38.52 
ey 135.1=275.20 . 24.68 
ef “  145.4=293.72  18.52—diff. between 2&4, 43.20 
6 *  153.8=308.84. 15.12 
160.2=320.36 11.52 
Swe ¢ 166.56331.70... 11.34 
at hI 20=341.78,., 10. os—diff between 4&8, 48.06 
. Aiéeording to Mr. Renwick, 
4 atmospheres, . . 291° ! ° 
Rissa? sa eariass 88 lodd Ans can difference, ‘sai neadOom 
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: 8% ») 
assigns it the following ratio, viz. 
Ferre? 
- At l}atmospheres, . . . . . 873 feet Ah second. 
2 pets pl {Wap genioupa TSEaOey * 
ARE EAE S LO5GKE SE OG VRE PAGESAM Caw 
6 PPE Gg ke: gE, SBR - 
s ts Bil G59: rea 
Wherefore, I conceive thd bom means “of safety is, in this as in other in- 
stances of liability of vie) pinbain to an pepniteciasiacnies ee force, to 
anticipate the cause and p 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 — 4 
water to the limits 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 I make a float of heavy plank, the specific gravity 
of which is about .900; or, preferably, of metallic plate or lead, 
made just buoyant by attaching cork securely to it, so that when 
raised out of the water in some dates it will operate as a weight, 
or power upon the short end of a lever, with which it is connected 
pres 
