202 REPORT— 1880. 



stations wherever photographic records similar to those at Kew are 

 obtained. 



Mr. Whipple was accordingly instructed by the Kew Committee to 

 write to the various observatories where declination magnetograpLs are 

 photographed, to ask thsLt fac-siviiles of the records taken at those stations 

 might be sent to the Kew Committee for compai'ison. 



In answer to this request, Dr. Hann, Director of the Observatory at 

 Vienna, and Senlior Capello, Director of the Observatory at Lisbon, have 

 kindly lent the original negatives, and Rev. Prof. S. J. Perry, Director 

 of the Observatory at Stonyhurst, and Dr. Da Souza, Director of the 

 Observatory at Coimbra, have kindly forwarded positives printed from 

 their original curves, and Dr. "Wild, Director of the St. Petersburg Obser- 

 vatory, has kindly forwarded very careful tracings of the St. Petersburg 

 photographs. These have been compared with one another, and with 

 the original negatives taken at the Kew Observatory, and much valuable 

 information has already been obtained. Other records have been asked, 

 but a sufficient time has not yet elapsed for them to come to hand ; it is 

 hoped that, as soon as they arrive, a complete discussion of them will 

 greatly extend our knowledge as to the causes of magnetic disturbances 

 over a considerable area of the earth's surface. 



A disturbance began at 4.20 a.m., Greenwich time, on the 3rd of March, 

 1879, which is described in the Stonyhurst record as ' a tremulous motion 

 of the declination magnet, which lasted for about thirteen hours, accom- 

 panied by a gradual increase of westerly declination.' 



About 5.80 a.m. the agitations west and east became greater, and at 

 7.30 a.m. there were sudden and great disturbances, the maximum 

 westerly declination being reached about 8 a.m. : again marked dis- 

 turbances, not quite so sudden, occurred just before 10 o'clock; then, 

 after a slight motion eastward until 10.30 a.m., there was again an increase 

 in the westerly declination, accompanied by great agitations, until 1 p.m., 

 after which there is a decrease in the westerly declination, and the dis- 

 turbance ends at about 5 p.m. 



During the whole time of this increase in the westerly declination 

 the agitations of the declination needle, including some twenty-four 

 maxima and minima values, ai'e absolutely coincident in time, and very 

 often equal in magnitude, at Kew and at St. Petersburg. 



At Stonyhurst also the curves are coincident with those at Kew 

 and are silmost facsimiles of them. 



On comparing the jihotographs at Coimbra and at Lisbon with those 

 at Kew -and at St. Petersburg, it is found that the agitations in Portugal 

 are not so clearly marked, but are coincident in time with those at the 

 other stations. 



Comparing the Vienna photographs of the same disturbance with 

 those at Kew, they are found to be almost facsimiles of one another — 

 every agitation westward or eastward at one place is coincident in time 

 with a similar agitation at the other. The Vienna jDhotographs are 

 remarkably clear, but the agitations are usually not so large as those at 

 Kew, and both are usually less than those at St. Petersburg, as given by 

 the tracings ; but the forms and periods of the successive agitations in a 

 disturbance, as well as the duration of the disturbances, are the same at all 

 the stations. 



Between 5 and 6 p.m. on the 3rd there was a disturbance, first east- 

 ward and then westward, at St. Petersburg, which was not felt at Kew ; 



