Sessional_Paper_1885-1886 — Page 145

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7. The most important improvement effected during the past year consists in the introduction on the 10th June of the rotating (dry and damp bulb) thermometers for regularly registering temperature and humidity at the Observatory. The figures exhibited in the respective tables during the previous inonths of 1885 were as far as possible reduced to the same standard by aid of observations made in different screens.

8. By aid of this apparatus the true temperature and humidity of the air round the Observatory is determined and not the temperature in any particular screen, which depends to such a great extent upon the position and form chosen for the latter. A perusal of the forthcoming volume for 1885 will show the advantage of adopting this apparatus at observatories within the tropics, and as it is adapted for use in the arctic regions as well as elsewhere, we are now enabled to make accurate and strictly comparable observations of temperature and humidity over the surface of the entire globe.

9. The thermometers are rotated day and night at as many hours as possible, the intermediate hours being derived from the thermograms using the rotating thermometers as standards.-At the same time tridiurnal eye-observations of thermometers exposed in a Stevenson's screen are made, by aid of which the errors committed by adopting this screen will be determined. This investigation besides its general interest will have its local importance, as a great number of meteorological stations in China have, at my suggestion, been furnished with wooden screens of a nearly similar pattern.- My experience so far shews, that the results obtained with Stevenson's screen are reliable when the screen is freely exposed to the wind, that the accuracy generally increases together with the force of the wind, and that the results are more or less erroneous when the screen is at all sheltered by any object even at a great distance. It would be advisable to adopt the rotating thermometer in making astronomical observations for the determination of the constant of refraction.

10. On the 1st of April the use of Morgan and Kidd's argento-bromide paper was introduced and was found a great improvement.-The sunshine-cards were from the 10th September to the 21st December changed at 10 h. 30 m. a. instead of at 10 h. 30 m. p. as was the case before and after those dates. The observations of clouds and particularly of the upper clouds being of so great importance for the physic of the globe, have been extended and are now made every three hours.

11. The time-service, which began on the 1st January 1885, will form the subject of a separate report.-The Lee Equatorial, which was transferred to this Observatory by the Astronomer Royal, was erected early in the year in a separate building, the cost of which was charged to Office Contin- gencies. Observations were made of Jupiter and his Satellites, Saturn and his Rings, and of a few Double Stars.

12. A new Observatory Standard Barometer was received in good order from Casella in London, and apparatus for investigating the temperature and induction-coefficients of magnets from Elliott Brothers, the latter being arranged so that either vertical or horizontal induction can be observed.

13. I attach some importance to the facility thus offered for re-determining the induction- coefficient, as it is known to sometimes change, and more especially in view of Chambers's comparison between two magnetometers, which gave different values for the force at Bombay Observatory. As the magnetometers give identical results when tested at Kew Observatory, the difference might be explained by changes in the induction-coefficients, which were not re-determined.

14. Notwithstanding the acknowledged superiority of Elliott's magnetometers, improvements could easily be introduced. The thermometers are not graduated on the stem, and it is so difficult to remove the one in the vibration box, that a reliable thermometer might with advantage be screwed into the roof of the box as was formerly done. The small telescope should be clamped on the stand and not left merely resting on the Y's, and much finer and stronger screws for adjusting the collima- tion could be cut in chilled bell metal.

15. As stated in the "instructions for making meteorological observations, &c.," meteorological instruments forwarded by observers, who regularly send their registers to the Observatory, are verified here free of cost. During the past year the following number of instruments has been verified and certificates issued:-

Barometers: 16 Thermometers: 40

16. At the end of 1884 the Swedish man-of-war Vanadis visited Hongkong and a party of the scientific staff under the direction of Captain RUDOLF NISSEN spent some days in making magnetic observations at the Observatory, which they chose as one of their principal observing stations, and their meteorological instruments were verified here.

17. Mr. HARDING, Assistant Engineer of the Imperial Maritime Customs of China, spent a week at the Observatory in April and received instruction in the erection of meteorological instruments and similar subjects.

18. A party of Officers under the command of Captain USBORNE MOORE made sextant observations of stars for time at the end of the year and compared with the standard clock. They also chose the anemometer-turret as the centre in their survey of the harbour.