INTRODUCTION.

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scending by their gravitating force, these,though perhaps not possessing strict ma-thematical correctness, will nevertheless besufficiently accurate for practice.

In this chapter I have also given ahistory of the various sorts of loco-motiveengines, as far as the extent of my enquiriesenabled me, which I have followed up byparticular descriptions, illustrated by draw-ings, on a copious scale, of the differentengines at present in use.

Chapter V.—Comprehends Experimentson the strength of cast and malleable ironrails, from which is deduced a practicalrule for determining the strength necessaryto carry different weights on other Rail-roads.

In Chapter VI. is si veil a series of

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