334 Review of Renwick 



in the literal meaning of the word, would be useless ; but when the 

 firemen wish to urge their fires more than usual, they understand 

 how to prevent the fusion of the plate, by directing a constant stream 

 of cold water upon it, so that in this point of view, perhaps we have 

 gained nothing."* 



We have extracted this passage at length from the essay of M. 

 Arago, because it appears to us that the subject of fusible metal 

 valves has not commanded among our countrymen the attention it 

 deserves. We do not learn indeed, that a single trial has yet been 

 made of them. And surely, the repeated and melancholy instances 

 of steam boat explosions, that have occurred among us during the 

 last two or three years, ought to awaken our attention to any de- 

 vices for securing safety, especially when recommended by authority 

 so respectable as that of M. Arago. There is some reason to fear 

 a growing apathy in the public mind on the subject of steam boat 

 accidents, from the very frequency of their occurrence. Those 

 who have often escaped, while others have fallen, fancy themselves, 

 like veteran soldiers, invulnerable. 



Professor Renwick recapitulates the chief precautions to be em- 

 ployed in order to insure safety, in the following paragraphs. Seve- 

 ral of them we have already mentioned incidentally, but the impor- 

 tance of the subject induces us to extract this passage entire. 



1. Cylindrical boilers, without any return flue, either without or 

 within, are safer than any others. 



2 Internal flues should be avoided whenever it is possible, and es- 

 pecially the chimney, or vertical flue, should never be permitted to 

 pass through the boiler. 



3. Every boiler should be furnished, in addition to the safety valve, 

 with one not under the control of the fireman. 



4. All boilers should be furnished with guage cocks, or other appa- 

 ratus, to show the level of the v/ater, and these should -be so placed in 

 steamboats, that no error in their indication can take place when the 

 vessel heels or rolls. 



5. Plates of fusible metal should be provided. 



6. A thermometer should be introduced into the boiler, whose in- 

 dications may be seen from without. 



7. Self acting feeding apparatus should be adapted to the boiler, 

 by which water will enter, and keep the fluid within at a constant 

 level, ^nd this should depend upon the waste of water, and not on the 

 action of the engine. It unluckily happens that no such apparatus 



'* Arago, on the Explosion of Boilers, in Franklin Journal, Vol. V. p. 410. 



