Page:Philosophical Transactions - Volume 095.djvu/58

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46
Dr. Herschel's Experiments on the Means

of the globules are also in this respect like the spurious disks of the stars; for they are proportionally lessened by increasing the magnifying power, and increased when the power is lowered.

(5.) When the estimations are compared with the powers,it will also be seen that the increase and decrease of the spurious disks of the globules is not inversely as the powers, but in a much less ratio.

 

11th Experiment.

Two other globules of different sizes were examined; and

With 706,3 they were pretty unequal.

With 522,7 they were considerably unequal.

With 303,8 they were very unequal.

(6.) This proves that the effect of magnifying power is unequally exerted on spurious diameters; and that, as with celestial objects, so with terrestrial, this power acts more on the small spurious disks than on the large ones.

 

12th Experiment.

I viewed a different artificial double star with 522,7, and keeping always the same power, changed the aperture of the telescope.

With the inside rays I found them considerably unequal, and 21/2 diameters of the largest asunder. The spurious disks are perfectly well defined, round, and of a planetary aspect.

With all the mirror open, they are also round and well defined.

With the outside rays, they are near 4 diameters of the largest asunder, and are also round and distinct, but surrounded with flashing rays and bright nodules in continual motion.