TRANSIT OF VENUS EXPEDITION.

Otago Witness, Issue 1191, 26 September 1874, Page 10

TRANSIT OF VENUS EXPEDITION.

Mr Bass, first assistant of the American expedition for the observation of the transit of Venus, which will take place on the afternoon of the 9th December next, has arrived in Dunedin by the San Francisco mail boat, in advance of Professor Peters, who is at the head of the expedition. Mr Bass is to select a suitable place for the observation, and in furtherance of this he will proceed in a few days on a tour through the Province, accompanied by the Chief- Surveyor. The Council of the Otago Institute has recommended the region of the Clyde, Dunstan, as being a likely locality to command an undimmed atmosphere and clear sky. The objections Mr Bass has to this district are that it would involve some difficulty and risk in the transit of the numerous delicate instruments with which the party will be equipped, and he is desirous of having a station as far south as possible. The instruments will consist of a large refracting telescope for the observation of the transit, with astronomical clock and chronometers, all adapted for being placed in circuit with telegraphic lines. There will also be a very complete photographic apparatus for noting the passage of the planet across the sun's disc. Portable buildings will be brought from America for the purpose of housing the observers and their instruments. This is only one of eight parties equipped by the American Government — five being assigned to the Southern Hemisphere and three to the Northern. The determination of latitude and longitude will form by far the greater part of the observations, and on this being accurately effected by the Americans in our own Province, aud by the Euglish expedition at Christchurch, an interchange of longitude by telegraphic signals will take place between the two parties. Our local observatory at Caversham — the longitude of which has already been carefully established by observation of the moon and culminating stars — will also be placed in connection and checked. A further and more elaborate interchange (necessaiily by means of chronometers) of longitudes will have to take place between the French expedition at Campbell Island, the German expedition at the Auckland Islands, and the New Zealand parties. The Americans will also undertake a comparison of longitude by means of numerous chronometers, between New Zealand and Melbourne. The expeditions of the different nationalities, it is proposed, will, after having deternined the positions of the points of their observations, meet in Melbourne in congress and arrange the taking of the differ ence of longitude between the Melbourne and Greenwich observatories by telegraph. Immediately the telegraphic cable i 3 laid between Australia aud New Zealaud the longitude of New Zealand will be verified by telegraphic signal under the direction of one of tbe expedition. The United States sloop-of-war, Swatara, has been specially fitted up and devottd to the distribution of the different parties in the Southern Seas, and Aviil make a circuit of the stations for that purpose. She sailed from New Yoik, under the command of Cap tain Ralph Chandler, on the Bth June, with the five southern parties aud their observers, She was to touch at Capetown first, to compare chronometers with the observatory at that place. Next she was to proceed to Crozet Island, where the first party, under the command of Capt. C. W. Raymond and Lieut. S. E. Tillinan, both of the U.S. Engineers, will be left. Thence she goes to Kergnelen Land, at which point a party under the command of Lieut. Ryan, and Lieut. Train, U S. Navy, will take station. Thence she proceeds to Hobart Town, Tasmania, which point will be occupied by a party in charge of Professor Harkness, of the U.S. Naval Observatory, and from there she goes directly to Bluff Harbour, where Professor Peters and his assistants will be landed. Chatham Island will be the last point of call, whore the fifth and last party, under Mr Smith, of the U.S. Coast Survey, and his assistant, Mr Scott, will be stationed. In the meantime, the vessel will mako a number of trips carrying chronometers to different places, and after the observations are over, she will proceed back and pick up the observers. She is expected to arrive at the Bluff on the Ist prox., but owing to the severe gales i*ecently in the Southern Ocean, she may be delayed until the latter part of the month. Apart altogether from the interest which all must feel in these great practical applications of science in finding a true determination of the distance between our planet and the sun, which is really the base line of astronomy, we have the practical and substantial advantage of having the position of several points so unmistakeably ascertained as to serve for all future time #f the initial ami ejosjpg pointy wbero.

with to test the accuracy of our Colonial trigonometrical surveys. Mr Bass, with the assistance furnished by Mr Thomson and Mr M 'Kerrow, of the Provincial Land Office, is making preliminary arrangements for the observations, and will proceed to Clyde on Saturday next.