May 28, 1 8 74 J 



NA TURE 



67 



will be placed at Christchurch. Since the idea of photo- 

 graphy has been introduced, two additional stations have 

 been added by the Indian Government under the super- 

 intendence of Col. Tennant, R.E. These are very com- 

 pletelv equipped, and will probably be situated the one 

 near Peshawur, the other at Roorkee. 



Besides these the observatories at Madras, Cape of 

 Good Hope, Melbourne, and Sydney will be utilised so 

 far as possible. The New South Wales Government have 

 voted 1,000/. for other observations in Australia. The 

 English Government have voted 15,000/. for all the expe- 

 ditions, but a much larger sum than this will be actually 

 required. It will be understood that the principal method 

 of observation is De I'Isle's, aided everywhere when pos- 

 sible by all the other methods except the heliometric. 



From the account that has been given of the difficulty 

 of determining the longitudes of the different stations it 

 will be seen that no little power of organisation is required 

 for the execution of the foregoing programme. All pre- 

 parations must be made for the observation of the moon 

 culminators. Alt-azimuths must be made, and also actually 

 \ invented for the express purpose. Nearly fifty chrono- 

 meters must be provided, and negotiations must be com- 

 pleted with telegraph companies. The photographic 

 operations have required the invention of a new photo- 

 heliograph, and the Janssen method of a new application 

 to it. The observations of contact have required the 

 purchase of a large number of equatoreals ; for each sta- 

 tion, besides having a 6-inch telescope, has also one or 

 more smaller instruments. One of the larger ones, made 

 by .Simms, is shown in Fig. 18. The transit instruments 

 have also been made expressly for this expedition. Be- 

 sides this all the accessories of these instruments had to 

 be provided. Huts for receiving them had to be made. 

 Forms for entering and reducing the observations had to 

 be prepared and printed. For some of the stations sleeping 

 arrangements, cooking apparatus, washing utensils, and 

 provisions had to be provided. Workmen, masons, and 

 assistant photographers, besides twenty-two observers, 

 had to he collected and trained to the work. When this 

 is considered it will be seen that no ordinary man could 

 fulfil all the duties. Fortunately we have in our 

 Astronomer Royal a man who combines to an exceptional 

 degree theoretical, mechanical, and organising powers ; 

 and we may safely say that the present expedition has 

 been completed under a generalship quite unparalleled in 

 the annals of Science. Sir George Airy has accomplished 

 all that was required in a manner that has call'd forth 

 the applause of those who have been connected v. ith the 

 preparations for this perhaps the most important astrono- 

 mical event of the century. We must congratulate ourselves 

 upon the fact that he has been most liberally supported 

 on all points by the British Admiralty. If we cannot 

 enter into the same details with regard to other nations, 

 it is only because we have not had the opportunity of 

 learning all the.ir actions. But we cannot conclude this 

 account of the British Government e.xpedition without 

 alluding to the valuable services which have been ren- 

 dered to it by Capt. G. L. Tupman, R.M.A., who has 

 spent the last three years in training himself and nearly 

 all the other observers in the use of the instruments, 

 seeing the instructions of the Astronomer Royal carried 

 out, ordering the stores, and in the most disinterested 

 manner looking after the expedition ; so that (as the 

 Astronomer Royal has lately pointed out) if the observa- 

 tions be successful their success will in a great measure 

 be due to his exertions. 



II. Besides the expeditions under the direction of the 

 British Government, another has been prepared which is 

 perhaps the most completely equipped one which has 

 ever been undertaken by a private individual in the inte- 

 rests of astronomy. Lord Lindsay has made prepara- 

 tions lo take up his position at i\Iauritius, provided with 

 means for utilising all the different modes of observation. 



He will combine his own results mainly with those of the 

 Russians ; and it is probable that no station could have 

 been found more suitable for a single obsei vtr to occupy 

 when so many different methods are emiif)yed. All the 

 instruments are of the most perfect description and made 

 by the best makers. The photographic meihod which he 

 will employ has been already described. The siderostat 

 has been made expressly for this purpose, and its surface 

 has been tested and found to be truly plane. Lord Lind- 

 say and his assistant Mr. Gill lay considerable stress on 

 the employment of the heliometer, and have discussed its 

 capabilities with great lucidity. They propose to make 

 observations of the external contact by the aid of the 

 spectroscopic method. The expedition will be provided 

 with about 50 chronometers, including one uncompen- 

 sated. These will be transmitted four times between 

 Aden and Mauritius. It is probable that they will also 

 connect the longitudes of the different stations on that 

 group of islands by chronometers. The German expedi- 

 tion at Mauritius will probably be connected with Lord 

 Lindsay's by a trigonometrical survey. Of these islands 

 two can be connected by direct signals with a heliotrope 

 reflecting the sun's light. From experiments made in 

 Russia, it appears that a signal may thus be seen in a 

 mountainous country with a clear atmosphere at a dis- 

 tance of 200 miles. There is little doubt then that the 

 longitude of each station on this group of islands will be 

 accurately known. 



III. — The Germans are sending out five or six expedi- 

 tions. At Cheefoo the accelerated ingress and retarded 

 egress will be observed ; at the Macdonald Islands the 

 retarded ipgress and the accelerated egress. The Auck- 

 land Islands will be favourable-for accelerated egress ; 

 Mauritius for retarded ingress, and Ispahan for retarded 

 egress. 



They will probably employ all the four methods at 

 most stations, viz. eye-observations of contact, heliometers, 

 photo-heliographs for the distance of centres, and also for 

 position-angles. There will be no photography at Mauri- 

 tius. Here will be employed four heliometers by Fraun- 

 hofer, 3 in. aperture, 3i ft. focus ; four equatorially-mounted 

 telescopes by Fraunhofer 4-i in. aperture, 6 ft. focus ; two 

 photo-heUographs by Steinheil, 5iin. aperture, and two 

 with quadruple object-glasses of 4 in. aperture. Besides 

 these, instruments are required for determining the local 

 time and the longitude ; for the Germans lay great stress 

 on De risle's method. For this purpose transit instru- 

 ments with diagonal telescopes on the Russian method of 

 23 in. aperture will be supplied, and alt-azimuths with 

 divided circles 12 in. to 14 in. diameter. The necessity of 

 determining the longitudes accurately has led the German 

 astronomers to consider carfully the best means by which 

 this can bo done. Dr. Auwers, to whom the direction 

 of the arrangements has been entrusted, has discussed the 

 matter in a very able manner. It appears from his in- 

 quiries that each group of stations will have their longi- 

 tudes very accurately determined. Thus the stations in 

 east Asia can be connected telegraphically. So also can 

 those about Alexandria ; also those about the Caspian 

 Sea and New Zealand. The group of islands near Ker- 

 guelen's, the Sandwich Islands group, and the Mauritius 

 group will be determined by chronometers. The only 

 difficulty is to connect these different groups. Many of 

 them will be compared with Greenwich indirectly by 

 telegraph. It is probable that Honolulu will be compared 

 by chronometers with San Francisco and Yokohama, thus 

 completing, as already mentioned, the telegraph and chro- 

 nometer connection round the world. In any case there is 

 little doubt that before the transit of Venus in 2004 the lon- 

 gitude of Honolulu will be determined by telcijraph. Since 

 Lord Lindsay intends to compare the longitude of Mau- 

 ritius with that of Aden by four chronometer expeditions, 

 aided by an uncompensated chronometer, there is little 

 doubt that the longitude of that group of islands will be 



