THE value of all service is in proportion to the number and extent of the benefits thence derived; that of the successful Navigator must therefore stand very high in the scale of public estimation: much also is due to the peculiar nature of this service, in the dangers it necessarily involves to those who adventure it; and hence it is that reward is justly due, even in cases wholly unsuccessful, although these are but rare; for if the main object be not obtained, the incidental discoveries in the search of it are in most instances sufficient to absolve the expedition from the charge of fruitlessness or total inefficiency. In that which constitutes the principal feature of the following memoir, the object was effected, so far as its progress could be conducted by its intelligent commander; and there can be no doubt, that had he lived, the evident zeal and ability he possessed would have produced the most satisfactory results. Having made these few preliminary observations, we shall now lay before our readers the following biographical sketch of the late Captain Tuckey, as transmitted to us immediately from his family.