I also think, however, that for reasons quite unconnected with the sliding-press, this pattern of room ought to be imitated in libraries hereafter to be built, and when this is the case, it must inevitably bring the Museum press after it. It will therefore be worth while to describe this style of building, in order that the mutual adaptation of it and of the sliding-press may be clear. It consists of three storeys lighted entirely from the top. It is therefore necessary for the transmission of light from top to bottom that the floors of the two upper storeys should be open; and they are in fact iron gratings. It follows that the floor of the highest storey must form the ceiling of the second, and the floor of the second the ceiling of the third. Here is the key to the sliding-press system. The beams or rods which I have described as projecting from the presses that line the wall already existed in the shape of the bars of the grating, and did not require to be introduced. Nothing was needful but to provide them with flanking ribs projecting at right angles, from which, as you see in the photographs, the additional press could be suspended by rollers, admitting of easy working backwards and forwards, and then the sliding-press was fully developed out of the skeleton door. No thought of it had ever crossed the minds of the original designers of the building; yet they could have made no better arrangement had this been planned with an especial view to its introduction. They had even made the storeys of exactly the right height, eight feet. I have not hitherto mentioned that the press takes books both before and behind, because this feature is not essential, and must indeed be departed from when the press is applied to the accommodation of newspapers and such like large folios. For ordinary books it is manifestly a great advantage, but carries with it the obligation that the presses shall not be higher than eight feet, or, when full on both sides, they will be too heavy to work with comfort, unless, which I do not think impracticable, machinery for the purpose should be introduced.