Sealed Tombs is a poem of negatives, not a negative poem. It maintains a positive description by defining subject matter through a set of boundary conditions. The confinement of possibilities gives opportunity for the reader or listener to interact and create their own image, making the experience a potentially positive experience. It also adds an element of risk, making the reader work harder to create their own vision of the subject.
The poem is not entirely consistent. The vocabulary becomes increasingly positive as the poem progresses, offering development from imagination to substance. The poem climaxes with the most clearly defined positive, the ironic negative action of gasping their curses.
Even so, there is still plenty of space for the reader to use the imagination by the use of ambiguity, for example “no spectres/ rattle the bones” offers the possibility that the bones are not rattled or that “no spectres” are doing the rattling. Now, I’m not sure what that means, but the possibilities have kept me thinking. Certainly, bones seem to be disturbed in most excavated tombs, either by natural actions such as earth movement, or by collapse of the framework that holds them in position or even internal decay.