According to Sir William Blackstone, a personal convenant may be transformed into a real, by the mere circumstance of the heirs being named therein, and having assets by descent from the covenantor. As they affect each other in the same deed, covenants may be divided into three classes. To ascertain whether covenants are dependent or not, the intention of the parties is to be sought for and regarded rather than the order or time in which the acts are to be done, or the structure of the instrument, or the arrangements of the covenant. When, in these cases, one party is redy and offers to perform his part, and the other refuses or neglects to perform his, he who is ready and offers, has fulfilled his engagement, and may maintain an action for the default of the other, though it is not certain that either is obliged to do the first act. Covenants are independent or mutual, when either party may recover damages from the other for the injury he may have received by a breach of the covenants in his favor, and when it is no excuse for the defendant to allege a breach of the covenants on the part of the plaintiff.
Covenants are affirmative and negative.
An affirmative covenant is one by which the covenantor binds himself that something has already been done or shall be performed hereafter. Such a covenant cannot be said to be performed until it becomes impossible to break it. On this ground the courts are unwilling to construe a covenant of this kind to be a condition precedent. The defendant, however, on a breach by plaintiff, might have his remedy by a cross-action of covenant. There is also a difference between a negative covenant, which is only in affirmance of an affirmative covenant precedent, and a negative covenant which is additional to the affirmative covenant.