Page:Science vol. 5.djvu/104

 {Vol. v.. Ho. HH

��lem|Krat.iiL'c of <!!IV'. 'I'hi^ (^stablialied llii? continuity of the riiu, and consequently the triitb of the tlcdnclion made from Jlie exami- nation of the tcmiH' rat urea of tlic waters of the Gulf of Mexico.

That part of the faribiiean Sea weat of the Island of Jamaica, ami the Pedro and llosalind banks, were thoroughly sounded in the winter of 1S80-81: and tlif Cayman Islands and the Misteriosa Dank wcic found to he part of a suh- inarine eslenaion of Ihe range running along the south-east side of Cuba.

Immediately south of these partially sub- merged peaks was an immense deep valley, extending from between Cuba and Jamaica as

���far as the Gulf of ilonduraa. This valley is narrow at its eastern end. but widens between the western end of Jamaica and Cape Cruz, where the soundings were 3,000 fathoms within fifteen milesof Cuba, and ^,«00 fathoms within twenty-five miles of Jamaiua. This valley is TOO miles long, with au average breadth of 80 miles. The greatest depth was 3,428 fathoms. just south of the Island of Grand Cayman. Between llisteriosa Bank and Chinchoiro Bank, the soundings were regular at 2,500 fathoms. N'orth of Misteriosa and Grand Cayman, to the Isle of Pines and Cape San Antonio, the soundings were generally 3,500 fathoms. So much for the western Carib-

The lines of deep-sea soundings taken by Li ent. -Commander Tanner in the Albatross last winter, were first from the east end of I'lu'rlo

��Rico to Bird l.slaud, thence nearly south to Trills idad, and then imrth-west towards the Mona J*assage. These liues, in connection with that which I ran with the Blake from the island of Dominica to Bird Island, aud back to Uonser- rat, clearly developed a submarine e1evati<ai, reacliing north and south nearly parallel to tl main chain of islands from Granada to St Christopher: the depth on this ridge being cousiderably less than 1.000 fathoms, with 1.500 and 2,000 fathoms on each side.

From the Mona I'assage a line was run to Los Roqnes. thence to the mainland, and then to Cnra^oa. The soundings south of this chain of islands gave a greatest depth of i ,030 fathoms. A line was run fVom Cura^oa to Beata Island, at the extreme south point of Santo Domingo. A line was also run from Morant Cays, off the east end of Jamaica, to the mouth of the Magdalena River, and llieu across the Rosalind Banks.

These several lines show an immense basin of nearly the same depth, extending from Santo Domingo and Puerto Uico to the shores of the Spanish Main, and over an area of more than 200,000 square miles, without any appar- ent inequality of surface, A line drawn from the west end of Sanlo Domingo to Cartagena shows a depth of 2,200 fathoms. The floor of the basin then rises gradually to the banks connecting the island of Jamaica with the Mosquito Bank. .

The basin is a few hundred fathoms deeper] in its eastern part, but rises abruptly to the' submarine elevation previously mentioned. A' very remarkable depression will be observed in the Atlantic, north of Puerto Rico. Lieut.- Commnndcr Brownson here obtained a deptli of 4,561 fathoms. Additional soundings will be taken, when a vessel is available, for more details over the ridge of which Bird Island forms a pari; but the general basin is prob- ably correctly [wrlrayed.

The soundings connecting the islands and t'arious banks, and to determine the tiepths of the western Caribbean, have already been made in detail. This work, so eminently with- in the iirovince of the navy, and performed with so much success by naval officers, should be continued, and I hojje to obtain many new soundings this summer.

The model also shows the elevations of adja- cent shores and islands. The horizontal scale is S-i miles to the inch; vertical, 6,000 feet or 1 ,000 fathoms to the inch. The latter, though so much distorted, was necessary to give the smaller elevations aud depressions.

Even with lliis scale, the hlgiietsl mountain

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