48 THE VOYAGE OF H.M.S. CHALLENGER. 



this purpose by the superintending electricians at those places. The observing station 

 at Malta was Spencer's Monument, and at Gibraltar the head of the mole in Rosia 



Bay, and the following were the results : — 



h. m. s. 



Meridian distance, by signals transmitted from Gibraltar to Malta, 1 19 29 '7 5 



Do. do. Malta to Gibraltar, 1 19 28 '54 



Mean meridian distance, . . . . ... . 119 29*15 



From which it appears that it took 0"60 s. to transmit the signal between the two places, 

 a distance of 1000 miles. 



The magnetic observing station at Gibraltar was in the middle of the garden of 

 the Main Guard, on the Neutral Ground. The observing station for rating chrono- 

 meters was the head of the mole in Rosia Ray, which is a much more convenient place for 

 this purpose than almost any other in Gibraltar, as, besides its seclusion, the sun is seen 

 there earlier in the morning than at the Ragged Staff, or the dockyard mole, a matter 

 of some moment when the easterly winds, so frequent in summer, keep the summit of 

 the rock constantly capped with cloud, for when this occurs, the town, the Ragged Staff, 

 and the dockyard are in the shade during the greater part of the forenoon, whilst the 

 sun is shining brilliantly on Europa Point, and nearly always as far north as Rosia Bay. 



On the 26th January, at 9 a.m., the vessel proceeded to the eastward of the Rock to 

 be swung for the errors of the compass and dipping needle. For the deviation of the 

 compass the ship was swung on the line of transit of Frayle Tower with Europa Light- 

 house, the true bearing of which had been previously ascertained. The error of the 

 dipping needle was ascertained by keeping the ship steaming slowly and steadily on a 

 given point of the compass, while observations were made for inclination, and these 

 observations were repeated on a sufficient number of points, to allow a curve to be drawn 

 from which the error could be ascertained for any part of the circle. The force of the 

 ship was ascertained by vibrating a needle on the four cardinal points, and comparing its 

 results with those obtained by the same needle on shore. These operations having been 

 satisfactorily completed, the ship returned to port to land letters, &c, and finally left at 

 6 p.m. for Madeira. 



Gibraltar to Madeira. 



Between Gibraltar and Madeira six soundings and three hauls of the trawl were 

 obtained, in depths varying from 1090 to 2600 fathoms (see Sheets 3 and 4). The 

 deposit at each of these Stations was a Globigerina ooze. The percentage of car- 

 bonate of lime ranged from 53 to 75, and consisted almost entirely of pelagic Fora- 

 minifera, Coccoliths, and Rhabdoliths. The residue, insoluble in weak acid, consisted 

 of a few Radiolarians, minute particles of quartz, felspar, augite, glassy volcanic frag- 

 ments, and clayey matter. 



