May 26, 1856.] FRENCH MARITIME SURVEYS. 147. 



The beautiful survey, by the officers of the French Etat-Major, of 

 the environs of Rome has been completed, but only one sheet has 

 as yet been published ; the remaining ones will, however, shortly 

 be in the hands of the public. 



French Maritime Surveys. — The maritime surveyors of France have 

 conducted their surveys along the coasts of Italy and of the Strait 

 of Gibraltar. M. Darondeau has completed the remainder of the 

 survey of Western Liguria ; and the whole coast of Italy may now, 

 be said to be completed from the Yar to the mouths of the Tiber, 

 and is in course of publication. M. Darondeau is now occupied in 

 conducting operations in the Neapolitan dominions, and has 

 already connected the islands of the Ponza group, with his triangu- 

 lation of the continent. 



The hydrographic expedition despatched by the French Govern- 

 ment to survey the Strait of Gibraltar and the adjoining coasts of 

 Morocco and Spain, has most satisfactorily completed its laborious 

 task, thanks to the zeal of Captain Kerhallet, well known by his 

 works on the Currents of the Atlantic and Pacific Oceans, and of 

 M. Vincendon Dumoulin, one of the most eminent of the corps of 

 Ingenieurs Hydrographes of France. The survey, based on an accu- 

 rate triangulation, extends from Cape St. Lucar on one side, and Cape 

 Spartel on the other, to Gibraltar, and on the northern coast of Mo- 

 rocco as far east as the Zafarina Islands. This excellent survey, I am 

 told, is now in the hands of the engravers. The most important results 

 of the operations of MM. Kerhallet and Dumoulin are the discovery 

 of several new shoals off the Spanish coast ; of an extensive rocky 

 plateau, from 15 to 18 miles in length, off Cape Trafalgar; and the 

 correction of various dangerous reefs between Cape Trafalgar and 

 Cadiz. But by no means the least important part of this survey, is the 

 determination of the depth of the Strait of Gibraltar, in olden times 

 supposed to be unfathomable, and continued so until the assumption 

 was dispelled by our able Mediterranean surveyor. Admiral Smyth. 

 The depth of this Strait has been considerably overrated in the 

 Spanish and English surveys, as it has been found in many parts to 

 average from 380 to 490 fathoms only ; the greatest depth being 503 

 fathoms (1010 metres) about mid-channel, at one mile east of the line 

 extending from Europa Point to Almina, at Ceuta. Numerous obser- 

 vations were made on the set of the currents in the Strait and on the 

 temperature of the sea at different depths, which dispel the belief in 

 an undercurrent setting out of the Strait. We must acknowledge with 

 gratitude to MM. Kerhallet and Vincendon Dumoulin this great addi- 

 tion to our store of improved hydrography and physical geogi'aphy. 



