June 17, 1880] 



NA TURE 



159 



1579, and of the red spot on Jupiter, have been examined, but 

 no certain results were obtained. Between 1S79, May 20, and 



1580, May 9, photographs of the sun were taken nn 145 day-, 

 and of these 270 have been selected for preservation. The 

 photographs show a complete absence of spots on 64 days out of 

 145, whilst in the preceding year there "as a similar absence of 

 spots on 121 days out of 150. The epoch of minimum appears 

 to' have occurred about the beginning of 1S79, and since last 

 October the outbreak of spots has been very marked." Various 

 spectroscopic and photographic results, it is stated, have been 

 communicated to the Committee on Solar Physics, with whom, 

 the Report states, the Observatory is in friendly communication. 



Under Magnetical and Meteorolo.;ical Instruments we are told 

 that the Thomson electrometer is in excellent order. " In the 

 warm weather of summer, and in winter w hen much artificial 

 heat is used in the basement, the photographs have been unsatis- 

 factory, but we are endeavouring to remedy tliis by cutting off 

 all communication with air from the basement. In the winter 

 the register was frequently interrupted by the freezing of the 

 water in the exit-pipe. A basin (with cesspool) has been recently 

 constructed to carry off the water discharged from this pipe. 

 The action of the photographic barometer appears to have been 

 improved by the slight changes mentioned in the last Report, 

 and small movements are in many cases excellently shown. A 

 new pressure-plate with sprmgs has been applied by Mr. Brown- 

 ing to Osier's anemometer, and it is jiroposed to make such 

 modification as will give a scale extending to 50 lbs. pressure on 

 the square foot. Other parts of the instrument have also been 

 renewed. An arrangement for slow motion of the barrel, which 

 was much wanted in adjusting the recording paper, has been 

 fitted to Robinson's anemometer. It is in contemplation to alter 

 the photographic cylinders of the magnetometers, barometer, 

 thermometers, and earth-currents apparatus, so as to make the 

 time-scales of all the magnetical and meteorological instruments 

 the same." 



Some intere-ting information is given under the head of 

 Reduction of Magnetical and Meteorological Observations. 



The following are given as the principal results for magnetic 

 elements in the year 1879 : — 



Approximate mean westerly 

 decUnation 



lS° 40' 



Mean horizontal force 



i 3'9U (in English units). 

 j I '803 (in Metric units). 



( 67 36 5 (by 9-inch needles). 



Mean dip < 67 36 54 (by 6-inch needles). 



( 67 37 47 (by 3-inch needles). 



"On the application of the Committee on Solar Physics, the 

 separate daily values of the diurnal range of magnetic declination 

 for the yearo 1S4S to 1S58 have been suppUed to Prof. Balfour 

 Stewart." 



The Report goes on to say: — "The Vioitors at their last 

 meeting suggested the advantage of preparing a digested account 

 of the magnetical results obtained at the Royal Observatory 

 from 1S41 to 1876, similar in some respects to the account of 

 meteorological results recently published. A beginning was 

 made by preparing the monthly means of diurnal inequality in 

 force and direction through the v\h3le period, and exhibiting 

 their combination in curves. It is known to the Visitors that, in 

 two communications to the Royal Society, I have exhibited 

 numerically and in curves the means of these monthly results 

 (yearly means through all months, and monthly means through 

 all years) as far as the year 1S63, In 1864 observations were 

 interrupted by the work in progress for the magnetic basement, 

 so that the reductions now to be made commence with 1S65. 

 The monthly results through the whole period being taken as 

 before, the next step, for obtaining exhibitions which the eye 

 and the mind could easily commarid, w as to collect the monthly 

 conclusions into a limited number of groups of years. On 

 inspecting the monthly curves in detail there was no hesitation in 

 fixing upon the following : — Fir.st group, 1S65 to 1S68 ; second 

 group, 1S69 to 1S72; third group, 1873 to 1S76. In each of 

 these, as before, yearly means are taken through all months, 

 and monthly means through all years. The curves in the second 

 group are strikingly larger than tho-e in the first and third ; the 

 linear dimensions of the curves of 1870 are fully j of those of 

 1876 in the east-and-west direction, and fully J in the north-and- 

 .=outh direction. In the study of the forms of the individual 

 carves ; their relations to the hour, the month, the year ; their 

 connection with solar or meteorological facts ; the conjectural 



physico-mechanical causes by which they are produced ; there is 

 much to occupy the mind. I regret that, though in contempla- 

 tion of these curves I have remarked some singular (but im- 

 perfect) laws, I have not been able to pur.-ue them. The heavy 

 load on the Observatory, and the limited means (in the present 

 year) of supporting it, will in part explain this." 



Under "Chronometers, Time-signals," &c., we are told that 

 during the period to which the Report refers the error of the 

 Westminster Clock exceeded is. on 120 days; on 32 of these it 

 was between 2s. and 3^'. , on 4 days between 3?. and 4s., and on 

 I day it exceeded 4s. 



"I have reason to believe," the Astronomer-Royal slates, 

 " thct the use of the time-signals, originating at the Royal Ob- 

 servatory, and distributed automatically from the General Post 

 Office, is becoming more and more extensive, and it seems 

 probable that the same system may be adopted by foreign 

 nations. Very lately an examination of our instruments was 

 made on the part of another country, with the view of establish- 

 ing something similar in one of their maritime cities ; and it was 

 intimated that Greenwich time would probably be used as stan- 

 dard. The establishment of time-balls, &c., at foreign ports is 

 increasing." 



With regard to the progress of the operations in connection 

 with the transit of Venus, 1874, it is stated that permission was 

 given by the Treasury to Major Tupman last September to 

 devote his time to the work till the end of June, 1S80. The 

 result is (taking the stations or station-groups in the order 

 which the Astronomer-Royal proposes for publication) : the 

 observations and calculations of the Sandwich or Hawaiian 

 group are completed ; those of the Egyptian group nearly 

 finished ; those of Rodriguez completed ; those of Kerguelen 

 nearly finished ; and also those (which unfortunately are less im- 

 portant) of New Zealand. "In January of the present year I 

 received through the Admiralty the notification of the Treasury 

 that the printing of the observations and calculations might pro- 

 ceed. It has gone on rather languidly ; but I have before me in 

 type 12S pag s, including the text and the greater portion of the 

 taljular part of the Honolulu work. I propose to take steps for 

 urging on this printing." 



" With regard to the transit of 18S2," the Report goes on to 

 state, " I have lately placed a memorandum before the Royal 

 Astronomical Society. From the facility with which the require- 

 ments for geographical position are satisfied, and from the rapid 

 and accurate communication of time now given by electric tele- 

 graph, the observation of this transit will be comparatively easy 

 and inexpensive. I have attached greater importance than I did 

 formerly to the elevation of the sun. For the four principal 

 phases (ingre s accelerated, and retarded; egress accelerated, 

 and retarded) I propose to rely mainly on : Isf, the Cape 

 Colonv ; 2nd, the shores of Canada and the United States, 

 Bermiida, and the We.st India Islands ; 3rd, the same as the 

 2nd ; 4th, the eastern shore of Au^tralia, or New Zealand in 

 preference if telegraph communication be made. I remark that 

 it is highly desirable that steps be taken now for determining by 

 telegraph the longitude of some point of Australia." 



The Astronomer-Royal makes tlie following statement in 

 reference to his own lunar theory : — " The general principle of 

 this is : to adopt for correction the best existing theory ; to 

 compute with the severest accuracy the numerical values of the 

 terms produced geometrically by the tabular coefficients, and also 

 the terms really due to the forces « hich produce them ; and to 

 remove the differences between these by corrections of the 

 tabular coefficients, for which corrections proper factors are 

 prepared. It was a special object with me to avoid the use of 

 powers of /// (a symbol well known to lunar theorists), and to 

 give easy means of computing, not new absolute values, but 

 corrections of existing numerical coefficients (a principle which 

 I have adopted extensively in other branches of astronomy), and 

 also of computing the effect of small external disturbances or 

 small changes of force. Both these are obtained by my process. 

 The heaviest part of the work is the severe computation to which 

 I have alluded, and this is done entirely by junior computers. 

 The calculations had been carried out in every part to the accu- 

 racy of 10-'; but for securing' the degree of accuracy which I 

 proposed it was found necessary to extend many parts to 10-^, 

 and some to 10-'. This has caused a very great addition to 

 the labour, but the work has advanced well, and will, I trust, 

 be finished ere long. While waiting for this, which is to give 

 the correction to every coefficient of the ordinary lunar theory, I 

 am employing myself partly in rearranging the whole work for 



