On the Relation of the Direction of the Wind to the Age of the Moon, as Inferred from Observations Made at the Royal Observatory, Greenwich, from 1840 November to 1847 December

XVI. On the Relation of the Direction of the Wind to the Age of the Moon, as inferred from Observations made at the Royal Observatory, Greenwich, from 1840 November to 1847 December. By G. B. Airy, Esq., Astronomer Royal. Received December 27, 1850,—Read March 6, 1851. In the year 1849, in a voyage to Shetland, I heard allusions to the belief entertained generally by Norwegian seamen, that a northerly wind may always be expected about the time of new moon. The expression of this belief was so positive, and the implication of the interests of the persons entertaining it was so distinct, that it appeared to me extremely probable that there was some physical foundation for it. At the first convenient opportunity, therefore, I took measures for discussing, with reference to this question, the directions of the wind at the Royal Observatory, during a period of rather more than seven years, as ascertained from the records of Osler's Self-registering Anemometer. I extended the research so far as to enable every reader to judge whether there is any probable relation between any Direction of Wind and any Age of the Moon. The collection and summation of the numbers was effected under the immediate superintendence of Mr. Glaisher. Great pains were taken to establish such checks on the operation that error is almost impossible. The general result is contained in the Table subjoined to this paper. And, while it shows that there is great uncertainty in the verification of an empirical law, even from nearly ninety lunations, it seems very distinctly to negative the asserted law which gave rise to the inquiry. In explanation of the Table, it is only necessary to remark that the civil day on which the new moon occurred is taken as the day of new moon (at whatever hour the conjunction occurred), and that the other days are counted in succession from it. The moon's synodic period being nearly $29\frac{1}{2}$ days, the month sometimes consists of twenty-nine days, sometimes of thirty, in almost equal proportions in the long run; and thus the numbers in the last horizontal row of figures must, to make them comparable with the others, be very nearly doubled. Although the sums of numbers in the other horizontal lines are not absolutely equal, they are so nearly equal that no remarkable error will be produced by assuming them as equal. Table exhibiting the number of hours during which the wind blew in each of sixteen equal divisions of the azimuthal circle, and also the number of hours of sensible calm, in the period extending (with very small interruptions) from 1840 November to 1847 December; from the records of Osler's Self-registering Anemometer at the Royal Observatory, Greenwich: arranged in reference to the days of the Moon's Age. | Days of the Moon's Age | N. | N.E. | N.E. | E. | E.S.E. | S.E. | S.S.E. | S. | S.S.W. | S.W. | W. | W.S.W. | N.W. | N.N.W. | Number of hours of calm. | Total number of hours for each day. | |------------------------|----|------|------|----|-------|-----|-------|---|--------|-----|----|--------|-----|--------|---------------------------------|----------------------------------| | 1 | 146| 52 | 84 | 42 | 80 | 6 | ... | 4 | 194 | 260 | 234| 282 | 128 | 32 | 40 | 386 | | 2 | 140| 58 | 86 | 66 | 54 | 4 | 6 | 26| 200 | 242 | 264| 174 | 78 | 34 | 74 | 90 | | 3 | 164| 80 | 52 | 36 | 32 | 12 | 32 | 166| 242 | 254 | 180| 84 | 32 | 36 | 84 | 502 | | 4 | 112| 88 | 48 | 18 | 56 | 10 | 18 | 44| 198 | 244 | 238| 220 | 100 | 22 | 14 | 74 | | 5 | 126| 58 | 62 | 34 | 104 | 22 | 10 | 26| 126 | 210 | 254| 250 | 78 | 44 | 44 | 52 | | 6 | 132| 46 | 110 | 76 | 66 | 20 | 6 | 30| 132 | 192 | 268| 214 | 98 | 46 | 46 | 86 | | 7 | 108| 66 | 84 | 72 | 102 | 12 | 26 | 20| 120 | 206 | 288| 148 | 176 | 28 | 44 | 54 | | 8 | 116| 72 | 96 | 58 | 66 | 18 | 4 | 14| 172 | 174 | 208| 278 | 124 | 46 | 56 | 56 | | 9 | 150| 78 | 64 | 48 | 68 | 30 | 10 | 28| 130 | 150 | 246| 244 | 96 | 56 | 48 | 80 | | 10 | 190| 62 | 106 | 32 | 98 | 18 | 18 | 36| 170 | 184 | 188| 152 | 138 | 44 | 36 | 74 | | 11 | 184| 76 | 88 | 52 | 66 | 16 | 10 | 22| 144 | 210 | 204| 212 | 120 | 20 | 54 | 76 | | 12 | 100| 92 | 98 | 66 | 50 | 12 | 6 | 22| 168 | 116 | 204| 264 | 146 | 44 | 26 | 48 | | 13 | 194| 72 | 68 | 58 | 74 | 18 | 12 | 32| 172 | 110 | 166| 170 | 104 | 44 | 46 | 76 | | 14 | 190| 72 | 60 | 80 | 78 | 24 | 20 | 34| 156 | 144 | 206| 164 | 82 | 24 | 66 | 86 | | 15 | 278| 86 | 68 | 60 | 86 | 30 | 34 | 30| 140 | 190 | 206| 148 | 104 | 30 | 32 | 64 | | 16 | 150| 84 | 50 | 104| 86 | 30 | 52 | 26| 84 | 158 | 252| 194 | 100 | 28 | 62 | 80 | | 17 | 208| 70 | 64 | 46 | 78 | 16 | 20 | 16| 136 | 166 | 244| 188 | 96 | 14 | 52 | 60 | | 18 | 212| 82 | 60 | 70 | 98 | 12 | 14 | 42| 128 | 194 | 188| 184 | 100 | 20 | 40 | 50 | | 19 | 228| 68 | 114 | 80 | 104 | 16 | 26 | 44| 64 | 86 | 166| 202 | 126 | 36 | 52 | 88 | | 20 | 174| 80 | 116 | 76 | 138 | 50 | 20 | 24| 92 | 114 | 176| 190 | 122 | 38 | 26 | 40 | | 21 | 168| 56 | 72 | 98 | 168 | 36 | 16 | 40| 88 | 140 | 216| 222 | 122 | 38 | 52 | 44 | | 22 | 206| 68 | 102 | 76 | 118 | 36 | 26 | 32| 74 | 150 | 170| 176 | 90 | 42 | 50 | 80 | | 23 | 224| 70 | 110 | 56 | 62 | 30 | 24 | 48| 180 | 126 | 196| 176 | 86 | 32 | 32 | 74 | | 24 | 236| 72 | 80 | 38 | 42 | 34 | 20 | 24| 140 | 156 | 242| 246 | 100 | 28 | 26 | 176 | | 25 | 206| 64 | 58 | 76 | 52 | 30 | 8 | 22| 124 | 202 | 238| 196 | 136 | 28 | 40 | 90 | | 26 | 126| 46 | 72 | 100| 70 | 18 | 16 | 14| 114 | 178 | 230| 164 | 164 | 30 | 56 | 78 | | 27 | 98 | 58 | 100 | 64 | 26 | 8 | 10 | 24| 192 | 210 | 286| 230 | 88 | 28 | 22 | 26 | | 28 | 88 | 68 | 48 | 68 | 74 | 28 | 32 | 50| 154 | 190 | 322| 286 | 92 | 22 | 30 | 50 | | 29 | 82 | 64 | 74 | 60 | 106 | 18 | 4 | 10| 180 | 198 | 220| 226 | 170 | 44 | 32 | 50 | | 30 | 80 | 26 | 32 | 30 | 20 | ... | 2 | 16| 96 | 124 | 110| 154 | 48 | 18 | 12 | 26 | Sum for each direction: 4816 2034 2326 1956 2226 634 482 832 4234 5276 6684 6144 3296 992 1246 2050 14942 60170 Royal Observatory, Greenwich, December 24, 1850.