178 A. M. Mayer—Effects of Magnetization, etc. 
experiment in illustration. The mirror was fixed so as to cause 
the cross hair of the telescope to cut the number 727 on the 
scale ; a cab passed while I was observing—the mirror quivered, 
obliterating the distinctness of the figure, and the scale slid 
apparently through the field of view, and became stationary at 
694. I went up stairs for a book; a cab passed, and on my 
return I found the cross hair at 686. A heavy wagon then 
passed, and shook the scale down to 420. Several carriages 
passed subsequently ; the figure on the scale was afterward 350. 
In fact, so sensitive is the instrument, that long before the sound 
of a cab is heard, its approach is heralded by the quivering of 
the figures on the scale. 
“Various alterations which were suggested by the exper'- 
ments were carried out by Mr. Becker, and the longer I worke 
with it the more mastery I obtained over it; but I did not 
work with it sufficiently long to perfect its arrangement. 
Some of the results, however, may be stated here. 
Figure of Scale. 
unmagnetized, - - 517 
“* magnetized, . - - 470 
“ “unmagnetized. - 517 
persist in the condition superinduced by the magnetism. 
passing of a cab in this instance caused the scale to move from 
517 to 534—that is, it made the shrinking 64 instead of 47. 
Tapping the bar produced the same effect. 
“The bar employed here was a wrought iron square core, 12 
inch a side and 2 feet long. 
“ The following tables will sufficiently illustrate the perform- 
ance of the instrument in its present condition. In each case 
are given the figures observed before closing, after closing, and 
after interrupting the circuit. Attached to each table, also, are 
the lengthening produced by magnetizing and the shortening 
consequent on the interruption of the circuit :— 
Circuit. 10 cells. || Circuit. 20 cells. 
Open, 647 ‘| Open, 653 
Closed, 516 131 elongation. || Closed, 475 188 elongation. 
Broken, 581 65 return. Broken, 579 114 return 
Open, 6 || Open, 638 
Closed, 509 128 elongation. || Closed, 452 186 elongation. 
Broken, 579 70 return. Broken, 568 116 return. 
Open, 632 Open, 632 : 
491 141 elongation. || Closed, 472 160 elongation. 
Broken, 568 77 return. || Broken, 561 
