544 



SCIENCE. 



[Vol. VII., No. 176 



brackish pools, or deposits of salt and gypsum. 

 The more extensive areas are called ' chotts.' The 

 first of these is the Chott-el-Fedjedj, the eastern 

 end of which is 12 miles from the shore of the 

 gulf, and separated from it by a ridge of drift and 

 limestone whose altitude at the lowest point is 150 

 feet. The surface of el-Fedjedj is nowhere less 

 than 48 feet above the sea. Toward the west it 

 is contracted in width somewhat by the encroach- 

 ment of the ridges which bound it on the north 

 and south. Beyond this point, which is about 70 

 miles from its eastern limit, it widens out, and is 

 known as Chott-el-Djerid. Here the surface is for 

 the most part level, and covered with an incrusta- 

 tion of salt, beneath which, in a few places, are 

 pools of water. The plain of el-Djerid is from 



MAP OF AFRICA, SHOWING THE RELATIVE SIZE OF THE 

 PROPOSED INLAND SEAS. 



50 to 200 feet above the sea-level. Its width from 

 north to south is about 45 miles. 



Near the north-west border of el-Djerid, and 

 separated from it by a ridge whose least altitude 

 is 550 feet, is the Chott Gharsa or Rharsa, whose 

 surface is from 30 to 35 feet below the level of 

 the sea. Gharsa is about 50 miles long and 20 

 miles wide. Beyond this chott to the west, and 

 separated from it by an insignificant elevation, is 

 a much larger depressed area, known as Chott 

 Melghigh or Melhrie. This is the basin referred to 

 as the site of the proposed interior sea. The area 

 which, lying below the Mediterranean, can possi- 

 bly be flooded by it, is represented by the shaded 

 portion on the accompanying maps. 1 Portions of 



1 The scale of the larger map is about 5S miles to the 

 inch. 



this area are 100 feet below the sea-level ; and 

 the average depth, if flooded, would be 78 feet. 



The figures above given exhibit the possible 

 dimensions of the 'flooded Sahara.' The united 

 areas of the two chotts over which the sea would 

 flow is, by Roudaire's measurements, about 3,100 

 square miles, less than half the area of Lake 

 Ontario. 



Throughout the remainder of the Great Desert 

 the elevation is considerable. Competent authori- 

 ties estimate the average height at 1,100 feet. Dr. 

 Lenz found, in travelling over many hundred 

 miles of the western portion of the Sahara, no 

 point of less altitude than 470 feet above the sea. 



The fact that marine deposits are found in many 

 parts of this area is, of course, a fact of no signifi- 

 cance in this connection. The skeleton of a whale 

 found in one of the highest cuttings of the Ver- 

 mont central railway is not regarded as an evi- 

 dence that the Green Mountains could now be 

 submerged by the waters of the ocean. 



The whale probably stranded there during what 

 geologists term the * Champlain epoch,' since 

 which time the surface has slowly risen. The 

 hypothesis that at least eighty thousand years 

 have elapsed since this epoch is believed by most 

 geologists to be well founded. Explorations across 

 the African desert justify the belief that the 

 marine deposits found there are not less ancient 

 than those of the Champlain period. 



To flood such a section with the sea, either the 

 next great subsidence must be patiently awaited, 

 or else an extensive system of pumping must be 

 resorted to.. The realization of the scheme of sub- 

 mergence (to accord with the popular estimate of 

 it), by either of these plans, may be regarded as 

 equally remote. 



The project of flooding the Sahara to the utmost 

 practicable limit can hardly be called a great one. 

 It is safe to say, that if executed, which is doubt- 

 ful, it will not sensibly affect the climate of south- 

 ern Europe. It will not create dangerous cm-rents 

 at Gibraltar, nor inconvenience seaports in any 

 part of the world. Geo. W. Plympton. 



LONDON LETTER. 

 A SUGGESTIVE report by Mr. W. H. Power, of 

 the Local government board, has just been pub* 

 lished, relative to the connection between scarlet- 

 fever and infected milk, — a connection which 

 has long been suspected. The farm in question 

 was sanitarily perfect, every modern improvement 

 in respect to cleanliness of vessels, and examina- 

 tion of persons employed, being in force. Mr. 

 Power was assisted in his investigation by Dr. 

 Klein : and their joint results leave little or no 



