was drawn across its whorls, and their widths were measured upon it in succession, beginning with the last but one. The measurements were, as before, made with a fine pair of compasses and a diagonal scale. The sight was assisted by a magnifying glass. In a parallel column to the following admeasurements are the terms of a geometric progression, whose first term is the width of the widest whorl measured, and whose common ratio is 1ôñ1804.
| Widths of successive whorls measured in inches and parts of an inch | Terms of a geometrical progression, whose first term is the width of the widest whorl, and whose common ratio is 1ôñ1804 |
|---|---|
| 1ôñ31 | 1ôñ31ããã |
| 1ôñ12 | 1ôñ1098ã |
| ãôñ94 | ãôñ94018 |
| ãôñ80 | ãôñ79651 |
| ãôñ67 | ãôñ67476 |
| ãôñ57 | ãôñ57164 |
| ãôñ48 | ãôñ48427 |
| ãôñ41 | ãôñ41026 |
The close coincidence between the observed and the calculated figures is very remarkable, and is amply sufficient to justify the conclusion that we are here dealing with a true logarithmic spiral.
Nevertheless, in order to verify his conclusion still further, and to get partially rid of the inaccuracies due to successive small {520} measurements, Moseley proceeded to inôÙvesôÙtiôÙgate the same shell, measuring not single whorls, but groups of whorls, taken several at