342 TRANSIT OP VENUS, 1874. EGYPT. 



Meridional Transits observed at Suez, 1874, December 18. 



LATITUDE of MR. HUNTER'S STATION at SUEZ. 



From the Admiralty Chart of the Port of Suez, the Latitude of the head of 

 the Southern Mole, at the entrance of the Maritime Canal, is stated to be 

 29. 56'. 3" North. 



Mr. Hunter's station, near the flagstaff of the Khedivial Chalet, was 4437 

 yards north of this point by the said chart, corresponding to 2'. 11"'7 of 

 latitude. Hence the Latitude of his station was 



29. 58'. i5" North.* 



DETERMINATION of the DIFFERENCE of LONGITUDE between the MOKATTAM and 

 SUEZ STATIONS by Exchange of GALVANIC SIGNALS. 



The observatories at Mokattam and Suez being in direct metallic con- 

 nection, telegraphic signals were exchanged between them on the nights of 

 1874, Dec. 4, 5, 7, and 14. 



The exchange on each night (with one unimportant exception) was con- 

 ducted in the following manner : A positive signal was sent from Mokattam 

 every 10 seconds, for about 15 minutes, by simply pressing the key in accord- 

 ance with the beat of a Solar chronometer. The movement of the galvano- 

 meter needle at Suez was recorded to the nearest tenth of a second by 

 estimation from the Sidereal transit chronometer. A similar series of positive 

 signals was then sent from Suez (using the Sidereal chronometer), and 

 similarly recorded at Mokattam (by means of the Solar chronometer). 



* For computing the final Equations for Suez, the latitude was assumed to be 29. 58'. 23". N., 

 which is sufficiently accurate. 



