52 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



therefore established within the case of the clock a siphon 

 barometer, on whose open end floats a rod whose rise and 

 fall with the varying atmospheric pressure moves a horizon- 

 tal lever at whose opposite extremity is supported a vertical 

 magnet. The corresponding falling and rising of this mag- 

 net, which is placed directly under the pendulum, causes a 

 variable magnetic attraction to be exerted upon the latter ; 

 so that with increasing density an increasing force of grav- 

 itation is, as it were, brought to bear upon the pendulum, 

 thereby slightly accelerating its movements and counteract- 

 ing the retarding influence of the atmosphere. Without this 

 arrangement it was found that a fall of one inch in the ba- 

 rometer caused an increase in the daily rate of the clock of 

 about three tenths of a second. The application of the grad- 

 uating maornet has also had a further advantage in causing 

 the arc of vibration to be sensibly constant at? all times. 

 12 A, XL, 431, and Aim. Rep>. of Astronomer Royal. 



RESULTS OF THE AMERICAN AND OTHER OBSERVATIONS OF 



THE TRANSIT OF VENUS. 



At the time of going to press with our last annual volume, 

 there had not been time to obtain precise information re- 

 specting the success of the various parties sent out to ob- 

 serve the Transit of Venus. We therefore give now a brief 

 account of the measures taken by our government with this 

 object, as well as of those of other nations, and an estimate 

 of the measure of success attained. 



As our readers may be aware, the American parties were 

 organized and sent out by a commission, composed of the 

 Superintendent and two professors of the Naval Observatory, 

 the President of the National Academy of Sciences, and the 

 Superintendent of the Coast Survey. All the responsibility 

 for the American system of observations rests with this com- 

 mission, which was created partly in order to secure the har- 

 monious co-operation of those departments of the govern- 

 ment which took an active interest in the matter. In this 

 respect the plan was entirely successful. Of the eight par- 

 ties organized, one was an army party, in which the chief 

 and assistant astronomer were officers of the Corps of Engi- 

 neers of the army. Besides this, the same corps furnished 

 the assistant astronomer for another party. There was also 



