Page:Scott's Last Expedition, Volume 1.djvu/437

1911] of air and earth is very great. The instruments are kept charged with batteries of small Daniels cells. The clocks are controlled by a master clock.

The instrument available for radio-activity measurements is a modified type of the old gold-leaf electroscope. The measurement is made by the mutual repulsion of quartz fibres acting against a spring—the extent of the repulsion is very clearly shown against a scale magnified by a telescope.

The measurements to be made with instrument are various:

The ionization of the air. A length of wire charged with 2000 volts (negative) is exposed to the air for several hours. It is then coiled on a frame and its rate of discharge measured by the electroscope.

The radio-activity of the various rocks of our neighbourhood; this by direct measurement of the rock.

The conductivity of the air, that is, the relative movement of ions in the air; by movement of air past charged surface. Rate of absorption of + and − ions is measured, the negative ion travelling faster than the positive.

Wednesday, May 17.—For the first time this season we have a rise of temperature with a southerly wind. The wind force has been about 30 since yesterday evening; the air is fairly full of snow and the temperature has risen to −6° from −18°.

I heard one of the dogs barking in the middle of the night, and on inquiry learned that it was one of the ‘Serais,’ that he seemed to have something wrong