xx GENERAL SUMMARY OF SCIENTIFIC AND 



pound compasses has afforded Sylvester occasion to show 

 that the problem of perfect parallel motion has at length been 

 solved, and the ingenious device of the French engineer has 



s ZD O 



enabled him to resolve several curious problems in geometry. 



ASTRONOMY. 



, The Transit of Venus. The Astronomical forces of the 

 world have continued to a great extent to be engaged in the 

 preparations for the observation of the transit of Venus oiij 

 the 8th of December, 1874, some details of which were given 

 in our last Annual Record, in so far as they had been a 

 year ago decided upon. In accordance with the general 

 plan proposed, the members of all the American parties met 

 at the Washington Observatory in the months of May and 

 June last for practice. Every instrument was set up precise- 

 ly as it is to be used in the actual observation, and the par- 

 ties were drilled in all the operations necessary at the sta- 

 tions. Photographs of the sun were taken with the appa- 

 ratus prepared by the commission, in the same way that they 

 would be taken during the critical hours of the transit. An 

 artificial representation of two sections of the solar disk was 

 set up about a thousand yards from the observatory, and 

 over this an artificial black planet was made to move by 

 clock-work. The apparent magnitude of this planet was the 

 same as that of Venus on the day of the transit, and, by 

 watching it with their telescopes, the observers familiarized 

 themselves with the aspect which Venus would present as 

 she entered upon the sun. 



The instruments for the five Southern stations left Wash- 

 ington for New York on May 30, and at the latter port were 

 shipped on board the United States ship Swatara, Captain 

 Ralph Chandler, which had been detailed to carry the par- 

 ties to their several stations. Captain Chandler sailed on 

 June 7, and, after a very fine passage, reached the Cape of 

 Good Hope on August 5. Stopping here ten days for sup- 

 plies, he sailed for the first station, which was Crozet Island. 

 Here, however, it was found impossible to effect a landing, 

 owing to the absence of a harbor, and the constant stormy 

 weather which prevailed during the time the ship could re- 

 main there. So far as known, all the other parties were suc- 

 cessfully landed, the stations being in Kerguelen Land, Tas- 



