useful purposes of life." If Professor Dewar's vacuum vessel can reduce
the heat-transmitting capacity of a vessel by almost ninety-seven per
cent., why should not the same principle, in modified form, be applied
to various household appliances--to ice-boxes, for example, and
to cooking utensils, even to ovens and cook-stoves? Even in the
construction of the walls of houses the principles of heat insulation
might advantageously be given far more attention than is usual at
present; and no doubt will be so soon as the European sense of economy
shall be brought home to the people of the land of progress and
inventions. The principles to be applied are already clearly to hand,
thanks largely to the technical workers with low temperatures. It
remains now for the practical inventors to make the "application to the
useful purposes of life." The technical scientists, ignoring the example
which Rumford and a few others have set, have usually no concern with
such uninteresting concerns.

For the technical scientists themselves, however, the low-temperature
field is still full of inviting possibilities of a strictly technical
kind. The last gas has indeed been liquefied, but that by no means
implies the last stage of discovery. With the successive conquest of
this gas and of that, lower and lower levels of temperature have been
reached, but the final goal still lies well beyond. This is the north
pole of the physicist's world, the absolute zero of temperature--the
point at which the heat-vibrations of matter are supposed to be
absolutely stilled. Theoretically this point lies 2720 below the
Centigrade zero. With the liquefaction of hydrogen, a temperature of
about -253 deg or -254 deg Centigrade has been reached. So the gap
seems not so very great. But like the gap that separated Nansen from the
geographical pole, it is a very hard road to travel. How to compass it
will be the study of all the low-temperature explorers in the immediate
future. Who will first reach it, and when, and how, are questions for
the future to decide.

And when the goal is reached, what will be revealed? That is a question
as full of fascination for the physicist as the north-pole mystery
has ever been for the generality of mankind. In the one case as in
the other, any attempt to answer it to-day must partake largely of the
nature of a guess, yet certain forecasts may be made with reasonable
probability. Thus it can hardly be doubted that at the absolut