. Carnegie Institution of Washington publication. 32 DISPLACEMENT INTERFEROMETRY BY TABLE 3. — Elongation of an iron rod, length 43 cm.; diameter cm. Factor 4-5Xio-7. = uojgauss. i H &e io6A//7 i H ke iof-A/// ampere gauss ampere gauss 81 2-3 253 - i-5 209 •5 3-9 429 - 132 3-7 i-7 7-7 847 -15-0 .80 88 2-7 7-7 847 -5-9 .40 44 7-7 847 3-9 429 - -3-8 7-5 825 -5-9 198 — — 3-9 429 - 9-5 -4-3 2-3 253 - i-5 198 — — 7 The curve in figure 33 crosses the axis (original length restored
. Carnegie Institution of Washington publication. 32 DISPLACEMENT INTERFEROMETRY BY TABLE 3. — Elongation of an iron rod, length 43 cm.; diameter cm. Factor 4-5Xio-7. = uojgauss. i H &e io6A//7 i H ke iof-A/// ampere gauss ampere gauss 81 2-3 253 - i-5 209 •5 3-9 429 - 132 3-7 i-7 7-7 847 -15-0 .80 88 2-7 7-7 847 -5-9 .40 44 7-7 847 3-9 429 - -3-8 7-5 825 -5-9 198 — — 3-9 429 - 9-5 -4-3 2-3 253 - i-5 198 — — 7 The curve in figure 33 crosses the axis (original length restored) in about the same strength of field as in figure 32. The curve is quite as clearly indi- cated, as may be expected (owing to the difficulties cited); but the higher observations (H=2oo) are decidedly smaller contractions than are seen in figure 32. The reason is to be found in the method of observation in triplets, where (curiously enough) the third reading (field zero) is an apparent contrac- tion in relation to the first reading in the absence of the field. The probable cause of this has been suggested above. Figure 33 seems to indicate that the curve is approaching an asymptote, or, in other words, that the susceptibility implied in equation (3) is FIG. 34. The apparatus in the preceding experiments was believed to be faulty in design, inasmuch as the clutch of the contact lever and of the coil were attached to the same rigid standard. This arrangement was therefore modified, so that the two mountings were quite independent, whereupon the anomalous results specified largely receded. The new data did not, however, differ essentially from the old and may therefore be omitted. As a second test a rod 28 cm. long of Swedish iron was inserted, the extra length being pieced out by brass tubing soldered to each end, so that the iron lay quite within the coil. The data obtained are given in figure 34, chiefly in relation to higher fields and obtained with mo
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