598
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IRE
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1862), and was advanced to brigadier- and major-general. Survey of South Africa has already measured in Cape and Natal, along the south-eastern shore of Africa, His division held the lines at Fredericksburg during the Colony from Cape Agulhas to Yaal river. It is therefore to be battle of Chancellorsville (May 1863), and he fought m expected that the triangulation will before long extend July at Gettysburg. As lieutenant-general in 1864, Farly from the Cape to the Zambezi. From this river to the crossed the Potomac in July, and part of his force ad- Bahr-el-Gazal, the 30th meridian passes through the terrivanced as far north as Chambersburg, Pa. He threatened tories of the Congo Free State, of German East Africa, Washington with his main force, but was compelled to retreat upon the arrival of the 6th corps, despatched by and of British East Africa, which it reaches near Albert Nyanza, crossing Lake Tanganyika, which is Grant from the front. In the ensuing autumn he won a Edward surrounded by hills visible from one shore to the other, partial success in the Shenandoah valley, but General this being a favourable circumstance to facilitate the work. Sheridan checked him in September at Opequan and Fisher’s Hill, and on 19th October he suffered a decisive The northern extremity of the African arc is in Egypt, and defeat at Cedar Creek. Wholly routed in March 1865, a triangulation performed along the Mediterranean shore Early was relieved of command, and took no further active would afterwards avail to link the African arc to the part in the war. After the peace he visited Europe, and Rumanian and to the Russian arc, so as to form a later resumed the practice of law, managing for a time continuous chain, ranging over 105° from Cape Agulhas with Beauregard the Louisiana lottery. He died at to North Cape. The question of the measurement of an arc in SpitzLynchburg, Va., on 2nd March 1894. bergen had already been raised by General Sabine. After Earth, Figure of the.—To complete, to link the exploration of that archipelago by Nordenskjold and together into one great network of triangles, the geodetic some others, it was resumed by Professor Rosen, who surveys accomplished in various countries, notably in prepared a scheme of triangulation, and the solution of France, England, Russia, and India, is the actual endeavour the problem was deemed possible, on'account of the imof astronomers, in order to reach an exact knowledge of provements of the base-apparatus of Taderin, whose nickelthe shape and size of the earth. From this common steel wire makes the measuring of an extended base-line desideratum the International Geodetic Association was much easier than by previous processes. During the summer of 1898 a private Swedish expediborn, which has promoted researches directly or indirectly relating to Geodesy. Planned as early as 1861, the I. G. tion, conducted by Taderin, began the reconnaissance of a Association grew slowly, and was definitely constituted by meridian chain between the parallels of South Cape and the Conventions of 1886 and 1895. The Association meets Ross Island, thus embracing about 4° 5' of latitude, between at least every third year, with the Central Bureau in Pots- 76° and 81°. The summits of the triangles were to be dam, and its president is Professor Helmert, Director of marked by signals on the shores of the Storfjord, of the the Royal Geodetic Institute, founded in 1868, the re- Strait of Hinlopen, and of the Seven Isles; the expedition succeeded in placing the signals from Ross Island to the sources of which are at the disposal of the Association. The general meeting of the I. G. Association at Paris Storfjord. The continuation of the work was then enin September 1900 gave the delegates an opportunity of trusted to two official commissions named by the Swedish knowing the state of the surveys in progress and pro- and Russian Governments, who proceeded to compose two jected.1 Among these undertakings may first be quoted missions. Towards the end of June 1899 the Russothe measurement of an arc of 66 degrees of amplitude Swedish expedition, on five steamships, went from Tromso which crosses Africa from the Delta of the Nile to Cape to Spitzbergen. The work was postponed till July, because Town; then the measuring of an arc in Spitzbergen, and of the ice and the time lost in erecting the cabins, and was then pursued till September. The Russian mission the remeasurement of the arc of Peru. The African arc will be surveyed along the meridian of took charge of the installation of the signals in the 30° E. Sir David Gill, director of the Cape Observatory, Storfjord. This was a very heavy task, on account of has already given a report of the operations undertaken in the elevation of the mountains around the gulf, and of its South Africa, which will form a good basis for the realiza- width, the two shores being seldom at the same moment tion of his admirable project. The Geodetic Survey of free from fogs; the consequence being that the sides of South Africa has established an important chain of tri- many triangles exceed 100 kilometres in length. It was angles between the 20th and 30th meridians; it will not also possible to do some astronomical and geodetical work be long before this reaches from Cape Agulhas to the for two of the most difficult summits, namely, those of Zambezi, embracing thus more than 20° of latitude. Cape Lee and of Whole Point, where a base-line has to MajorLaffan and LieutenantWettstein, English and German be measured. At the north the condition of ice did not commissioners, have recently measured, under the direction permit reaching the Seven Isles; the Swedish mission has of Sir D. Gill, a chain of triangles along the 20th been employed in measuring a base-line at Hekla Hook meridian, which divides Bechuanaland from German South- and determining some summits. In September both West Africa, between Rietfontein and the parallel of 22° missions settled in winter stations; the Russians at Hornsouth latitude. Mr Alston has united, by a chain along sund, on the south-western coast of Spitzbergen, in 77 the 28th parallel, through Bechuanaland, those already N., the Swedish in the Treurenberg Bay, towards 80 . established along the 20th and 24th meridians. The They remained there, isolated from the outer world, during Chartered Company had a triangulation along the 30th nine months, occupied in astronomical and meteorological meridian undertaken in Rhodesia, and the Geodetic observations. When the spring of 1900 came, the geo Survey of Rhodesia achieved, amid great difficulties, the detical work was resumed and pursued till September, observations between Mangwe and the parallel of -19°, amidst very unfavourable circumstances. They succeeded and reconnoitred the northern part of the chain up to with much ado in building up on Mount Chydenius the Zambezi, when the war in South Africa caused the (alt. 1500 metres) a signal destined to join the chain interruption of these works. As soon as circumstances of the Storfjord to that of Hinlopen Strait. . The revision of the arc of Peru, the opportunity for whicd permit, the chain of Rhodesia will pass through the had already been pointed to by Mr Davidson, the delegate Transvaal and be linked with that which the Geodetic of the United States to the I. G. Association m 188y, 1 and later by Mr Preston in 1898, has been undertaken, See the valuable reports of Lieut. Perrier and Professor Helmert.
