few days later. The southerly motion of the planet after greatest elongation and the fact that it is in the portion of the orbit south of the ecliptic cause a rapid diminution of the interval between the setting of the Sun and of the planet, and it can be seen only a few days after the middle of July. It passes inferior conjunction with the Sun and becomes a morning star on August 12th, It then moves rapidly toward greatest west elongation (18° 12') and reaches this point on August 29th. It then rises an hour and one-half before sunrise, and it will be an easy object to see in the morning twilight for a week or so before and after the end of August. Venus is an evening star setting a little more than two hours after sunset on July 1st, and less than an hour and three-fourths after on August 31st. It is still increasing in apparent distance from the Sun and will continue to do so until September 20th, but its motion among the stars is along a line farther and farther to the south of the Sun's position and this causes a hastening of the time of setting, which more than counterbalances the retardation due to increase of apparent distance from the Sun. Mars is still an evening star on July 1st, but is too near the Sun to be seen. It passes conjunction with the Sun and becomes a morning star on July 15th, but does not move far enough away to be seen in the morning sky until nearly the end of August. It does not reach its maximum distance from the Earth until a fortnight after conjunction, since it is still receding from the Sun and will not reach its aphelion until the middle of October. Jupiter is a morning star rising about an hour before sunrise on July 1st, and shortly after midnight on August 31st. It moves about 13° eastward among the stars from the eastern part of Taurus into Gemini, and at the end of August is south and west of Castor and Pollux, the brightest stars of the latter constellation. Saturn is getting around into fair position for evening observation. It rises at about 11 P.M. on July 1st, and shortly before 7 P.M. on August 31st. It will reach opposition early in September. Its motion during the two months' period is westward and southward about 3° nearer the boundary line between Aquarius and Pisces. There are no bright stars near it. Uranus rises shortly after 7 P.M. on July 1st, having passed opposition with the Sun on June 28th. By the end of August it rises about three P.M. It is therefore well up in the southeastern sky by the time twilight has disappeared. It is in the constellation Sagittarius and moves about 2° westward during the period. During August it is about 2° north of Lambda Sagittarii, the third magnitude star in the handle of the milk dipper. It is just within the limit of naked eye visibility for ordinary eyes on clear moonless night. Neptune passes conjunction with the Sun on July 2d, and becomes a morning star. It is in the western part of Gemini. NOTES FROM PACIFIC COAST OBSERVATORIES. LICK OBSERVATORY SEISMOGRAPH RECORD OF APRIL 18, 1906. The intensity of the earthquake shock of April 18th at Mount Hamilton was less than the average intensity in the surrounding territory; on the unmodified* Rossi-Forel scale, it should be rated as about VII. In destructive violence the shock was not as severe as the local one of August 2nd, 1903, which received only passing notice outside Santa Clara County. The difference lay in the relation of displacement to time of displacement. The amplitude was several times as great in the recent earthquake, but the oscillation was much slower. Smooth vibrations with double amplitude of one or two centimeters (one-half or three-quarters of an inch,) pass unnoticed by the keenest observer, if their period be five seconds or more. Rapid or abrupt motions of onetenth this amplitude are felt as sharp shocks. The Ewing three-componentt seismograph of the Lick Observatory gave a very satisfactory record, though the instrument was not designed for so great displacement and did not register all the motion. Professor OMORI has pronounced the record as of great value. The north-south record is broken in two places; its three parts are marked N.S. or (N.S.) on the the accompanying reproduced tracing. The most remarkable north-south features are the long swings past the center of the plate and the indications of a wrench which seems to have jarred the pendulum from its bearings for a time. The vertical record leaves much to be desired. About ten seconds after the beginning, the pendulum was thrown from its bearings by the horizontal force of the heavy shock that also interrupted the north-south record, and was lodged against the standard. First, however, it registered a drop of nearly four centimeters, (one and one-half inches.) The east-west record is nearest complete, though the pen frequently passed beyond the cir *Nature, 42, 349, 1890; Publ. A. S. P., 7, 123, 1895. +See illustrated description of early forms of this instrument in Encycl. Brit.. article Seismometer. |