Dividing the period of lunation into quarters, with the time of syzygies and quadratures as the centres of these quarters, he found that the earthquakes were distributed as follows.
| Totals | Syzygies | Quadratures | Difference in favour of the Syzygies | |
|---|---|---|---|---|
| 1843–1847 | 1,604 | 850·48 | 753·52 | 69·96 |
| 1848–1852 | 2,049 | 1,053·53 | 995·47 | 58·06 |
| 1853–1857 | 3,018 | 1,534·13 | 1,483·87 | 50·26 |
| 1858–1862 | 3,140 | 1,602·99 | 1,537·41 | 65·98 |
| 1863–1867 | 2,845 | 1,463·42 | 1,381·58 | 81·84 |
| 1868–1872 | 4,593 | 2,333·48 | 2,259·52 | 73·96 |
| 1843–1872 | 17,249 | 8,838·03 | 8,410·97 | 427·06 |
The reported earthquakes between 1751 and 1843 are shown to conform with the same rule.[101] Julius Schmidt, astronomer at Athens, found for the earthquakes of Eastern Europe and adjacent countries for the years 1776 to 1873 that there were more earthquakes when the moon was in perigee. Other maxima were at new moon, and two days after the first quarter. There was a diminution at full moon, and a minimum on the day of the last quarter. As one example of results which are antagonistic to the general results obtained by Perrey may be quoted the results of an examination by Professor W. S. Chaplin of the earthquake recorded at the meteorological observatory in Tokio. The list of earthquakes, 143 in number, extending over a period of three years, was recorded by one of Palmieri’s instruments. The results were as follows:—
1. There have been maxima of earthquakes when the moon was two and nine hours east and seven hours west. At the upper transit there is a minimum.
2. Considering the moon’s position with regard to the sun, at conjunction there were 32, at opposition 37, and at quadrature 74. East of the meridian the maximum was at least four hours.
3. When the moon was north of the equator these were 68, when south 82.
4. A maximum of earthquakes seven and eleven days after the moon’s perigee. The fact that these results were obtained for the earthquakes of a special small seismic area renders them more interesting.[102]
Frequency of earthquakes in relation to the position of the sun.—The question as to whether there is a connection between the frequency of earthquakes and the relative position of the sun is to a great extent identical with the question as to the relative frequency of earthquakes in the various seasons. It is a subject which we find referred to by writers in the earliest ages. Pliny and Aristotle thought that earthquakes occurred chiefly in spring and autumn. In later times it has been a subject which has been most carefully considered by Merian, von Hoff, Perrey, Mallet, Volger, Kluge, and others who have devoted attention to seismology. In a résumé of the earthquakes of Europe, and of the adjacent parts of Asia and Africa, from a.d. 306–1843, Mallet gives the following results:—
| For Nineteenth Century | For the whole period | |||||||
|---|---|---|---|---|---|---|---|---|
| Winter Solstice | 177 | } | Solstices | 253 | } | Solstices | ||
| Spring Equinox | 151 | } | 306 | 170 | } | 403 | ||
| Summer Solstice | 129 | Equinoxes | 150 | Equinoxes | ||||
| Autumnal Equinox | 164 | 315 | 159 | 329 | ||||
The above periods were called by Perrey critical epochs, because as a general result of his researches he found that at such periods there was a greater frequency of earthquakes. Fuchs, quoting from Kluge’s tables, extending from 1850–1857, tells us that the recorded earthquakes occurred as follows:—