INDUSTRIAL PROGRESS DURING THE YEAR 1873. xxiii 



the official astronomers of all civilized countries, and which 

 must continue to engage it for some time to come, is the tran- 

 sit of Venus over the disk of the sun, which is to occur Decem- 

 ber 8, 1874. This phenomenon is not visible either in Amer- 

 ica or Western Europe, as it begins several hours after the 

 sun has set in Washington on December 8th, and ends several 

 hours before it rises on the 9th. To see it, parties must be 

 dispatched to Asia, and to the islands of the Indian and Pacific 

 oceans; and the organization and equipment of these parties 

 form a labor demanding great care and foresight from all 

 who have it in hand. The governments of Russia, Germany, 

 France, England, and America are all making preparations 

 on the most extensive scale to observe the phenomenon, and 

 it is likely that one or more of the minor nations will join as 

 auxiliaries. The Russians Avill occupy some twenty-five sta- 

 tions scattered throughout the eastern half of Siberia. Three 

 different methods of observation are proposed, all of which 

 will be employed ; but only one method will be applied at 

 any one station. These three methods are : 



1^ Co'ntact observations, in which the exact moment at 

 which the dark body of Yenus enters wholly Avithin the 

 bright disk of the sun is carefully noted. 



2. Heliometer measures of the apparent angular distance 

 between the limbs of Venus and the sun, taken during the 

 whole time that the planet is projected on the sun. 



3. Photographing the sun with Venus on its disk as often 

 as possible during the transit, and afterward measuring these 

 photographs. 



The Germans will also employ all three methods of obser- 

 vation. They propose to send a party to Pekin, and to oc- 

 cupy Kerguelen's Land in the Indian Ocean, one of the Auck- 

 land Islands, south of New Zealand, and also Mauritius. The 



rench propose to equip six stations, but the modes of obser- 

 vation seem to be left to the choice of the parties themselves. 

 Little is known of the state of their preparations. The En- 

 glish, under the lead of the Astronomer Royal, are disposed 

 to depend mainly on contact observations. But Mr. De la Rue, 

 the most successful astronomical photographer of England, 

 has been urging the propriety of photographic determina- 

 tions, and several photo-heliographs are being put into oper- 

 ation under his direction for use at the various stations. 



