324 Review of Renwick 
After principles have been studied in the abstract, we love to see 
them brought i into near connexion with the arts which they illustrate, 
and we. renew our acquaintance with them with increased ale 
Si we recognise them in their useful applications. 
- The article on Combustion, in the second chapter, is particularly 
seis of attention -and we know not where to find, within the same 
compass, more useful information c n this important Takia not mere- 
ly in reference to the Steam Eng ~ but to the sages 5 sine 
of life. 
We do not propose to follow our author through all parts of his 
- work, but shall have chiefly in view those parts wile are at present 
peculiarly i interesting to the community, namely, the méans of — 
5x safety in the use of the Steam Engine. 
- The dangers of the Steam Engine are obviously of a twofold ak 
acter,—such as result from defective construction of the machinery, 
and such as arise from the peculiar nature of the moving, force. ‘The 
work before us begins with the. consideration of the former,.particu- 
larly as it relates to the construction of boilers: We the an eX- 
tract on the materials of boilers. ‘ 
Batters are always of metal, and three different materials are used 
in their construction: wrought i iron, cast iron, and copper. rought 
iron and copper are rolled for this purpose into plates and sheets, 
which, after being bent to the proper form, are united by bolts, driven 
through holes punched around their edges, and riveted. When eas 
iron is-used for boilers, ‘they may either be of a’single piece, OF ‘it 
may be cast in separate portions, which are united by screw ape an 
nuts, passing through holes left or drilled in flaunches.- Of t 
copper is most easily worked, but it is by far the most exe 
1, and is. therefore now used only in a few instances, where the 
others are, from the circumstances of the case, inadmissible. . Gopper 
is much less easily aeted. on by oxygen, than sheet irons, it acts 
less powerfully on the saline deposits, that occur when sea or ofher 
impure water is used; in addition, : it is less liable, than either of the 
other materials, to split or crack on sudden changes of temperature. 
Sheet iron is more tenacious than copper, but is liable to rapid oxida- 
tion, and has frequently invisible joints arising from the manner in 
which it is manufactured. Still; however, when the water used is 
tolerably pure, it is the best material, if we take into view the strength 
and eapeeive weeitern Bi 67. 
& 
- 
