The individual, however, who attempts so much, is in hazard of attempting more than any individual can well perform. For, besides this, he has to make another effort quite distinct--in the investigation of facts. All the needed scientific knowledge he may possess; but the same sufficiency of local or topographical knowledge is not supposable. The work so produced, therefore, cannot easily avoid the defects, either of error in the details of some branch, of unequal development of the parts, or of a superficial treatment of the whole. Against these dangers some writers have had recourse to assistance, inviting contributions from others favoured with better means of information than themselves; and to them attributing, in so far as they assisted, the entire merit and responsibility of the work. This transference of responsibility is warranted by the necessity of the case--but it is unusual; and as it scarcely occurs except in works of the kind in question, it may happen that even a professing judge of such works, if the habit of attention be not good, may entirely overlook the circumstance. In the _Statistical Account of Scotland_, the obligation to individual contributions has been carried to the greatest extent; indeed, it is simply a collection of such contributions, and nothing more. This part of the plan was necessitated by another, in which the work is equally peculiar--namely, the distinct treatment of smaller divisions of the country, than have been taken up in any other work of the kind, having an entire country for its object. To obtain a body of parochial statistics, it was necessary to have recourse to persons well acquainted with the bounds, and intelligent, at the same time, upon the various subjects of inquiry. But to find such in nine hundred parishes would, of itself, have required much of that local knowledge, the want of which was the occasion of the search--had there not been a class or order of men among whom the desired qualification, in many points, might be supposed to be pretty generally diffused; and from whose favour to a project of public usefulness much aid might be expected. It was in this manner that the co-operation of the parochial clergy came to be suggested.