Note 2 — Chapter VII · THE MARCH OF SCIENCE

In the meantime, portable energy will no doubt be achieved in ways other than electrical. Some very interesting compressed-air tools are already in limited use. Holes are drilled and rivets driven by little contrivances which have a store of force within themselves furnished by compressed air. One of the many uses of the cheap oxygen and hydrogen, and doubtless of cheaply liquefied gases of high-resisting power,2 will no doubt be to work various kinds of machinery. This use of liquid airs has been much derided, and indeed a good deal of nonsense has been written as to its possibilities, drawing from a recent and accomplished writer the remark that “The statements which have sometimes appeared in the daily papers, announcing impending revolutions in the methods of obtaining cheap power by the application of liquid air, have originated from an imperfect comprehension of the problems involved.”3