Page:Light waves and their uses.djvu/160

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142

��Light Waves and Their Uses

��method. The actual micro-metric measurements which have been made of these satellites with the largest telescopes give results which vary considerably among themselves. Hence the interest in trying the interferometer method. The appa- ratus used was similar to that shown in Fig. 103, i. e., it consisted of two movable slits in front of the objective of the eleven-inch glass at the Lick Observatory.

The atmospheric conditions at Mount Hamilton while the work was in progress were not altogether favorable, so that

����FIG. 103

out of the three weeks 1 sojourn there there were only four nights which were good enough to use, though one of these nights was almost perfect ; and on this one night most of the measurements were made. The results obtained, together with those of four determinations which have been made by the ordinary micrometer method, using the largest telescopes available, are given in the following table:

��Number of Satellite

�A. A. M.

�Ens.

�St.

�Ho.

�Bu.

�I

�1.02 0.94 1.37 1.31

�1.08 0.91 1.54

1.28

�1.02 0.91 1.49 1.27

�1.11 0.98 1.78 1.46

�1.11

�II

Ill

�1.00 1.78

�IV

�1.61

��The numbers in the column marked A. A. M. are the re- sults in seconds of arc obtained by the interference method. The other columns contain the results obtained by the ordi- nary method by Engelmann, Struve, Hough, and Burnham

�� �