Page:Philosophical Transactions - Volume 095.djvu/62

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50
Dr. Herschel's Experiments on the Means

925,4 nearly equal, and 21/2 diameters of the largest asunder.

706,3 nearly equal, and above 2 diameters of the largest asunder.

432,3 pretty unequal, and 2 diameters of the largest asunder.

177,0 considerably unequal, and 11/4 diameter of the largest asunder.

I examined also two other drops, with different apertures, without changing the power, which was 706,3.

With the inside rays they were very little unequal, and 3/4 diameter of the largest asunder.

With the outside rays they were considerably unequal, and 11/4 diameter of the largest asunder.

From what has been said, it appears that all the, remarks which have been made with regard to the spurious disks of the silver globules are confirmed by the luminous spots on the drops of quicksilver. There is a difference in the proportion which the spurious disks on quickisilver bear to the drops, and that on the silver globules to the size of the globules; the latter also give a greater variety of colours and magnitudes than those on quicksilver; these are circumstances of which it would be easy to assign the cause, but they can be of no consequence to the result we have drawn from the experiment.

16th Experiment, with black and white Circles.

I tried to measure some of the spurious disks by projecting them on a scale with a moveable index, but found their diameters were too small for accuracy by this method; for this reason I had recourse to artificial measuring-disks, and prepared a set of eleven white circles on a black ground, and eight black ones on a white ground. In order to guard against