student would command all the tools of his trade ... The same applies to universal philosophy ... Many branches of study can thus be prosecuted quite privately, and in the closest retirement." Doubtless, but there are "rarities, specialities, researches which require the aid of powerful machinery." One half of historical work may now be done in private, with limited resources, but only half; the other half still presupposes the employment of such resources, in the way of repertories and documents, as can only be found in the great centres of study; often, indeed, it is necessary to visit several of these centres in succession. In short, the case stands with history much as it does with geography: in respect of some portions of the globe, we possess documents published in manageable form sufficiently complete and sufficiently well classified to enable us to reason about them to good purpose without leaving our fireside; while in the case of an unexplored or badly explored region, the slightest monograph implies a considerable expenditure of time and physical strength. It is dangerous to choose a subject of study, as many do, without having first realised the nature and extent of the preliminary researches which it demands; there are instances of men struggling for years with such researches, who might have been occupied to better advantage in work of another character. As precautions against this danger, which is the more formidable to novices the more active and zealous they are, an examination of the present conditions of Heuristic in general, and positive notions of Historical Bibliography, are certainly to be warmly recommended.
CHAPTER II
"AUXILIARY SCIENCES"
Let us suppose that the preliminary searches, treated of in the preceding chapter, have been made