Frequently the examination of an abstract will disclose minor defects, imperfect descriptions, invalid instruments, and abortive attempts at conveyance, which, while not reaching the merits of the title, nor yet, in many cases, casting any suspicion upon it, still tend in a measure to obscure it. These defects are generally known as "clouds upon the title."

As a general rule, a deed, hen, charge or incumbrance of any kind, to cast a shadow upon title so as to give the owner relief in equity, must be one that is regular and valid on its face, but is, in fact, irregular and void from causes or circumstances that have to be proved by extrinsic evidence. If the invalidity plainly appears on the face of the instrument, or, although not apparent on the writing, if it is shown by any of the preliminaries that attend it, or in any of the links which connect it with the title, so that no lapse of time or change of circumstances can weaken the means of defense, such an instrument does not, in any just sense, even cast a cloud upon the title or diminish the security of the owner of the land. The rule in such cases is, that an instrument of this character can work no mischief, and hence, no occasion arises for equitable interference for its removal or cancellation.