The use of ‘source-books’ in historical studies has been justified by experience: the imagination can hardly fail to be quickened by the living voices of the past. In addition to this purpose—the provision of colour and the heightening of the personal aspect, we have another—the smoothing of the approach to a highly technical subject. Naval History is so different from land History, and sailing ships are so different from steamships, that the subject abounds in pitfalls. The belief is still common that the ‘big ships’ of the Armada were defeated by ‘cockleshells’ manned by volunteers; plans of battles still appear in which ships are shown sailing straight into the wind; the strategy of blockade is frequently discussed in the abstract, apart from its practical problems. The cure for such misconceptions lies in concrete illustrations of the limiting conditions of sea warfare. Many of the points emphasized may at first seem trivial: unless they are made vivid, they are not realized to be vital. If we appear to lay too much stress upon administrative defects, we would remind our readers that they only heighten the fame of the admirals who triumphed in spite of them.

It is obvious that a book of this size can in no sense be exhaustive, but can deal only with certain aspects: there are large gaps which must be filled by the text-book, which this selection is intended to supplement, not to replace.