Page:Philosophical Transactions - Volume 095.djvu/57

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of ascertaining the Magnitude of small celestial Bodies.
 

8th Experiment.

The luminous spots, of spurious disks of the globules were of unequal diameters. The globule No. 1 had the largest disk, and the smaller ones the least; and the gradation of the sizes followed the order of the numbers.

(2.) This agrees with the spurious disks of celestial objects: the stars of the first, second, and third magnitude having a larger spurious disk than those that are of inferior magnitudes.

 

9th Experiment.

I found that there was a considerable difference in the colour of the spurious disks; one of them was of a beautiful purple colour, another was inclined to orange, a large one was straw coloured, a small one pale-ash coloured, and most of them were bluish-white.

(3.) With respect to colours, therefore, the terrestrial also agree with the celestial spurious disks.

 

10th Experiment.

I made two globules of different diameters, and placed them very near each other, so that their spurious disks might resemble those of a double star; this succeeded perfectly well. I viewed them with different powers.

With 177 the vacancy between them is 3/4 diameter of the large star.

With 232, it is 11/4 diameter.

With 303,8, it is 15/8 diameter.

With 432,3, it is 13/4.

(4.) This experiment proves that the spurious diameters