520 KANSAS CITY REVIEW OF SCIENCE. 



telescope precisely on Venus by means of its computed place in space, as found 

 in that admirable work, the " American Ephemeris." To parties not famiHar with 

 these things, we have to say that of course Venus was invisible, but we placed the 

 telescope accurately on the unseen world by the aid of two gradua'ed circles of 

 metal called the Right Ascension and Declination circles, which are rigidly 

 attached to their respective axes on the equatorial. 



These, in connection with a sidereal c'ock, enable one to set the telescope on 

 any invisible celestial object whose position is catalogued. Thus : any star can be 

 found at noon, as well as at night, the observer not looking at the sky to find the 

 object, but upon the verniers near the ruled edges of the measuring circles. 



By this method the glass was placed on Venus before it came in sight be- 

 tween the earth and sun, in order that precious time might not be wasted in ad- 

 justment when it made its appearance. 



At yh. 59m. the sun was still obscured, but the cloud had nearly passed to 

 the east, light appearing on its western side with increasing brilliancy, when at 

 8h. the sun burst into view. 



Instantly we began close scrutiny, striving to detect the first indentation on 

 the solar edge by the advancing world. A watch regulated with great precision, 

 and indicating mean Washington time, was placed on the telescope close to the 

 solar eye-piece, so that a reading of its seconds' hand could be made in an in- 

 stant. There were three time-pieces in the observatory, all regulated with care. 

 One read sidereal ; another, mean Washington, and the other mean solar time at 

 New Windsor. 



Through the kindness of Vice-Admiral Stephen C. Rowan, U. S. N., Super- 

 intendent of the Naval Observatory at Washington, and the courtesy of the West- 

 ern Union Telegraph Company, we received accurate time by telegraph direct 

 from the mean solar clock at the observatory in Washington, hearing its seconds' 

 pendulum beat in New Windsor. These time signals were sent at mean Wash- 

 ington noon on December 4th, 5th, 6th, and 7th, by direct circuits to receiving 

 observatories. This was a work requiring great care and skill on the part of the 

 •officers, since receiving stations were in all directions from Washington, but 

 must receive the signals at the same instant of absolute time from the same 

 clock. 



We insert the scheme for the transmission of time, devised by the American 

 Transit of Venus Commission, and put into successful execution on the days men- 

 tioned. We quote from the circular issued by the Commission to observatories : 

 " The signals to be sent out by the observatory are wholly automatic, and consist 

 of a series of short breaks, so made in a closed telegraphic circuit as to represent 

 the beats of a mean-time clock. 'They begin at iih. 56m, 30s., and close at i2h. 

 om. OS., Washington mean time. During the interval there is a break at the be- 

 ginning of every second, except that in each minute the breaks corresponding 

 to the 29th second, and to the 55th, 56th, 57th, 58th, and 59th, seconds are omit- 

 ted. Thus, the first break after the pause of five seconds always marks the be- 

 ginning of a minute, and the first break after the pause of one second marks 30 



