CRITICAL NOTICES OP NEW PUBLICATIONS. 327 



cleansing of the boiler. This is impracticable in the connected boilers 

 before referred to, when used on board of steamers ; and the fact 

 may serve to explain the frequent explosions which occur in the 

 United States, on the Mississippi river. It is to this kind of boiler 

 that the third mode assigned by which unduly heated metal may be 

 produced is applicable. This form is condemned by the Committee, 

 and is not in use, we believe, for our steamers. We wish they may 

 be successful in preventing the further extension of its use in their 

 own country. When the deck of the steam vessel is inclined by pas- 

 sengers moving to one side, by wind, &c., the upper boilers are more 

 or less emptied of water ; they are thus exposed to the fire, without 

 the protection of a covering of water, and become unduly heated. The 

 water which is forced into them on the return of the boat to its pro- 

 per position is thrown upon the heated metal and flashed into steam. 



For a connected view of the conclusions drawn from the discussion 

 of this part of the subject we would refer to the Report itself. One 

 of the articles in which these are exhibited contains a table of alloys 

 applicable to boilers working at pressures from one to thirteen atmo- 

 spheres, and is deduced from experiments by the Committee, in which 

 much labour must have been encountered, and in the course of which 

 some curious properties of alloys appear to have been developed. The 

 temperatures given in this table as corresponding to the assumed pres- 

 sures are from data drawn up by the Committee from their own ex- 

 periments. This differs considerably from that lately given by a 

 Committee of the French Institute. The results, however, are the 

 mean of many experiments, in which the data appear to have been 

 calculated with care. The pressures increase more rapidly with the 

 temperatures than in the table of the French commissioners, agreeing 

 more nearly with the experimental results of Dr. Ure and Professor 

 Robison than with those of other experimenters. 



3rd. Explosion may arise from defects in the construction of 

 the boiler or of its appendages. 



Under this head are discussed the influence of the form, material, 

 and manufacture of a boiler. The waggon boiler is considered as ap- 

 plicable only when low steam is used. Boilers with interior flues 

 commonly give way by blowing off the heads of the boiler, or by the 

 flattening of the flues. Those in which the flues pass through both 

 heads of the boiler are, cceteris paribus, the most safe, while 

 those in which the flue passes through the steam chamber and 

 top of the boiler are liable to accident. Weakness arising from irre- 

 gular forms, from the cutting out of the metal by rivets, from the 

 wearing of the junctures of the plates when exposed to the fire, &c., 

 are discussed. Frequent proving of the boiler is recommended, 

 while in use, as the only means of being certain of its retaining the 

 strength shewn in the preliminary proofs before its use. 



The Committee consider it important that several valves should be 

 placed in the induction and eduction pipes of the forcing pump which 

 supplies the boiler with water, in order to prevent the derangement 



