Eptiome of the electro-meteorological and magnetic observations, experiments, etc. made at the Kew Observatory / [Sir Francis Ronalds].

  • Francis Ronalds
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: Eptiome of the electro-meteorological and magnetic observations, experiments, etc. made at the Kew Observatory / [Sir Francis Ronalds]. Source: Wellcome Collection.

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    of the principal experiments which had been made; and of the whole electro-meteorological journal. The chief contents of which compilation were printed in the volume of the Society reports for 1844, (p. 120, et seq.) with the exception of the voluminous tables of observations, of which specimens only were given. % 2nd. Vol. On the 1st of January, 1845, the three Registering electrometers were ap¬ plied to the clock work of the electrograph, in lieu of the resinous-plate by which means the series of two-hourly electric observations for the whole 24 hours could be rendered complete. In the beginning of 1845, a new modification of Coulomb's torsion electrometer was completed, whereby observations on atmospheric elec¬ tricity (or other) can be made at all times, and under circumstances (of humidity, &c.) which render the use of former constructions troublesome and unsatisfactory ; but in windy weather the tremor of the pedestal and high conductor in the electrical observatory was found to interfere too much with its regular employment. In April, 1845, the Storm-clock, now in the electrical observatory, and which empowers an observer to set down multifarious events occurring in very rapid succession, was finished. A valuable suggestion con¬ cerning it, and the loan of a journey-man clock from the Greenwich Ob¬ servatory, were obligingly furnished by the Astronomer Royal. The Pluvio-electrometer, a large copper dish supported by an insulat¬ ing glass-pillar, warmed by the usual lamp, &c. and placed upon a pe¬ destal on our roof, was constructed in this year, and employed in June, 1845, in the observation of a singular fact, viz. that, without rain, this dish was, during about 26 minutes, in a positive state, whilst the high conductor was negatively charged, but rain was impending. In the same month, 1845, Kreil’s Barometrograph arrived, and after a slight addition had been made, was set to work experimentally. On the 12th of June, 1845, the wooden Balance-anemometer gave place , to a much more solid and complete apparatus (of brass). The journal in this Volume begins August 1, 1844, and ends June 18, 1845. It went on as usual until the end of 1844. From the 1st January, 1845, fourteen electric observations are generally recorded daily, viz. one at every even hour, one at sun-rise, and one at sun-set. The recorded two daily minima and two daily maxima are derived from these 14 ob¬ servations. The new experiments were as follow, viz. In February and March, 1845, on the different effects produced by two atmospheric conductors, whose insulators were situated at different heights above the earth, but whose upper extremities had the same height above the earth. This set of experiments was made to prove that a difference in construction of the Greenwich and Kew apparatus caused some of the difference in the values obtained from each. On March 19th, 1845, the principal conductor was removed from its glass pillar, in order to test the permanence of the insulating power, which was found to remain entirely undiminished. A charge of 100 degrees of Volta decreased to 3 degrees in 12 hours. In May, 1845, a striking example of atmospheric electrisation without insulation, occurred. It was an instance of the St. Elmo fire, I believe, and my attention was first called to it by Mr. Galloway. In June, 1845, I made a plan and elevation for erecting an electric
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