Report of the Kew Committee. 



213 



Several additional sets of observations of Absolute Declination have 

 been made with the view of investigating certain changes in the 

 values of the torsional effect of the suspending thread upon the deter- 

 mination of the true position of the magnet employed. 



The magnetograph curves made use of in the preparation of the 

 tables of diurnal range of Declination (see Appendix, Table III) have 

 been drawn from the original photographs by means of an eidograph 

 kindly lent by Captain W. J. L. Wharton, F.R.S., the Hydrographer. 



Magnetic Reductions. — At the request of Professor Balfour Stewart, 

 F.R.S., copies of the Kew declination disturbances for the years 

 1858-1865, together with the daily wind values for the years 1858 to 

 1869, have been made and forwarded to him; the Rev. S. J. Perry has 

 also received copies of the records of certain selected days of magnetic 

 disturbance for 1886. 



KraJcatoa Eruption. — In May last, at the request of the Krakatoa 

 Committee of the Royal Society, a memorandum was prepared for 

 that body on the magnetic effects recorded at the various observatories 

 over the globe which occurred at the time of the great explosion of 

 August 27, 1883, in the Straits of Sunda. 



Magnetic Stations. — A list of all known magnetic stations has been 

 prepared jointly by General Sir J. H. Lefroy and the Superintendent 

 for publication by the Committee of the British Association on 

 magnetic reductions, and will be published in the Annual Report for 

 the current year. 



It contains references to all localities on the surface of the globe 

 where continuous observations of terrestrial magnetism have been 

 made for periods of at least one month in duration, and gives, together 

 with the geographical position of the stations, references to the publi- 

 cations where the results of such observations are to be found, as well 

 as the names of the authorities, whenever these could be ascertained. 



Falmouth Magneto graphs. — At the request of the Secretary of the 

 Royal Cornwall Polytechnic Society, the specifications for the magneto- 

 graphs supplied to the Falmouth Observatory last year, which were 

 drawn up by Mr. Whipple, have been revised and printed with illus- 

 trations in the Annual Report of that Society for 1886. 



Sectional Lines. — In addition to the sectional lines obtained for the 

 purpose of plotting down magnetic observations on the international 

 scale, as suggested by General Sir J. H. Lefroy, and as mentioned in 

 last report, the Committee have had a number of copies struck off 

 from the stone on tracing paper for the use of observers who may 

 desire to make tracings of existing curves on the same scale. 



II. Meteorological Observations. 



The several self-recording instruments for the continuous registra- 

 tion respectively of atmospheric pressure, temperature, and humiditv, 

 VOL. XLIII. r 



