The quantities in the sixth column of this Table represent the sums of those in the four preceding columns, and are taken as the ordinates in curve b, fig. 6, while those in the last column are the same quantities multiplied by 100/83-6 so as to express the intensity of the heat at each point in percentages of that at the centre, and are represented by curve c in the same figure. With these quantities as ordinates the curve c has been laid down. In this reduced curve the ordinates represent the relative intensities of the radiation of heat. The time which the sun's diameter took in transit on the 12th October, 1890, the day on which the photograph was taken, was 130 seconds, but as the sun's image was 800 mm. in diameter, and the diameter of the aperture of the radio-micrometer was 2 mm., the interval between the first and last contact with the limb is longer than this byth of the time of transit. The whole time between the first and last contacts is, therefore, 130.3 seconds.

We thus obtain the following results :

In the first and last columns are given the distance of a point from the sun's centre taking its radius as 100. The second and sixth contain the values of t. In the third and fifth are given the corresponding values of the heat radiated, the mean of which will be found in the fourth column. These values, down to D = 75, agree in a remarkable manner with those obtained by Langley, using the bolometer, and beyond that are in as close agreement with this distinguished observer's results as could well be expected in view of the fact that they are based on a single photograph.

This close agreement seems to show that the method is a most reliable one, and the ease and rapidity with which the curve may be