He had hers all ready to put on, and when the necessary changes and investments had been made, Zaidie found herself clad in a costume which was not by any means unlike the diving-dresses of common use, save that they were very much lighter in construction.
The helmets were smaller, and not having to withstand outside pressure they were made of welded aluminum, lined thickly with asbestos, not to keep the cold out, but the heat in.

On the back of the dress there was a square case, looking like a knapsack, containing the expanding apparatus, which would furnish breathable air for an almost unlimited time as long as the liquefied air from a cylinder hung below it passed through the cells in which the breathed air had been deprived of its carbonic acid gas and other noxious ingredients.
The pressure of air inside the helmet automatically regulated the supply, which was not permitted to circulate through the other portions of the dress.

The reasons for this precaution were very simple.

Granted the absence of atmosphere on the moon, any air in the dress, which was woven of a cunning compound of silk and asbestos, would instantly expand with irresistible force, burst the covering, and expose the limbs of the explorers to a cold which would be infinitely more destructive than the hottest of earthly fires.

It would wither them to nothing in a moment.
A human hand or foot--we won't say anything about faces--exposed to the summer or winter temperature of the moon--that is to say, to its sunlight and its darkness--would be shrivelled into dry bone in a moment, and therefore Lord Redgrave, foreseeing this, had provided the breathing-dresses.