The **bolograph** thus obtained must be cleared of the absorption of the earth's atmosphere, and that of the transmitting apparatus - a spectroscope and siderostat.

If we assume that the **bolograph** of solar energy is simply a graph of amorphous radiation from an ideal radiator, so that the con- Temperature stants cl, c 2, of Planck's formula determined terrestrially apply to it, the hyperbola of maximum intensity is XO = 2, 921 X 10 7; and as the sun's maximum intensity occurs for about X =4900, we find the absolute temperature to be 5960° abs.