August 23, 1877] 



NATURE 



353 



of citric acid, ''as much acetic acid, and 3 grammes of pyro-gallic 

 acid ; an atom of nitrate of silver is added. The negative is 

 placed in this developer and left in it till the coloration of the 

 image becomes sufficiently intense ; then it is passed into a bath 

 of hyposulphide of soda, then washed and dried between leaves 

 of blotting paper. It is then proof against heat and moisture, 

 and may be kept indefinitely in an album. The apparatus itself 

 is so constructed as to be capable of remaining two days in water, 

 even in sea water, without deterioration. 



The most important papers read at the meetings of the 

 Kharkov Society of Naturalists during 1876 are: — "On the 

 Mechanism of the Respiration of Birds," by N. Byeletsky ; 

 "On Respiration of Roots," by A. Zaykevich ; two entomo- 

 logical papers on the province of Kharkov, by P. Ivanov 

 and V. Varoshevsky ; "On the Arachnidce Arenea; and on 

 the Conjunction of C/ila»iydo»io>iai ptilvirulus and Stigloclo- 

 mum," by L. Reinhard ; and the continuation of the "Flora 

 of Ukraina" {Composila^ to Saholaceic), by K. Gornitsky. 



Mr. Thomas S. Cayzer, head-master of Queen Elizabeth's 

 Hospital, Bristol, known as the author of one thousand arith- 

 metical tests and of other approved school-books, has made a 

 complete collection of the principal passages in Latin authors 

 that refer to our island, and editing them with vocabulary and 

 notes, is about to issue the volume through Messrs. Griffith and 

 Farran, as a Latin reading-book, illustrated with many wood- 

 cuts and a map, under the title of " Britannia." 



The additions to the Zoological Society's Gardens during the 

 past week include a Slow Loris ( Nycticebus tardigradus) from 

 India and a Cape Hedgehog (Erinaceits frontalis) from West 

 Africa, received in exchange ; a Wedge-tailed Fruit Pigeon 

 (Ticroii sphcnura) from India, presented by Mr. A. H. Jam- 

 rach ; an Egyptian Gazelle {Gazella dorms) from Barbary, 

 presented by Capt. J. Graham. 



AN ALGERIAN INLAND SEA 



A S our readers are aware several schemes have recently been 

 •'*■ before the public for the creation of an inland sea in North 

 Africa, one of the most ambitious and most impracticable of 

 these being the floodmg of a great part of the Sahara. Another 

 scheme which has engaged the attention of the French Govern- 

 ment for some time is much more feasible and likely to be 

 attended with good results. The Report of a Commission on 

 the plan proposed by .M . Roudaire for the creation of an inland 

 Algerian sea was recently presented to the French Academy of 

 Sciences by M. Fave, and as it contains several points of scien- 

 tific interest, we propose to lay it before our readers. 



Since the French domination was extended in the province of 

 Constantine as far as the town of Biskra, the attention of several 

 observers has been turned t'l the very marked depressions of the 

 soil, which commence at about 50 kilometres to the south of 

 Aures, that is, to the border of the Sahara, and extending from 

 east to west. M. Virlet d'Aoust supposed, in 1S45, from the 

 measurement of the slope of a river discharging into the Chott 

 (or marshy lake) Mel-Rir, that the bottom of that chott must be 

 below the level of the Mediterranean. In 1S49 M. Dubocq, a 

 mining engineer, proved, by a very numerous series of barometric 

 observations, published in 1S53, that singular anomaly, which 

 Capt. Vuillemot confirmed in 1S56. It was reserved to Capt. 

 Roudaire, to render the fact incontestable and to determine the 

 depth with almost complete accuracy. 



After having taken for his starting-point the einboiichure of one 

 of the two small streams which fall into the sea at the bottom of 

 the Gulf of Gabes, M. Roudaire traversed the steppe of 

 Gales, 46 metres high, then arrived at the depression of a chott 

 the surface of which he estimated, at sight, at 5,000 square 

 kilometres. He then reached, by crossing a second elevation of 

 45 metres, that of Krilz, the depression of the Chott Rharsa, 

 situated to the east of the Chott Mel-Rir, from which it is 

 separated only by two elevations of small height. These two 

 slight elevations bound the Chott Asloudj, the surface of which 



does not exceed So square kilometres. The surface of the Chott 

 Rharsa has been estimated at 1,350 square kilometres ; that of 

 the Chott Mel-Rir, which has been surrounded by a polygon of 

 levelling, contains 6, 700 square kilometres. The three basins 

 which form the Chotts El Djerid, Rharsa, and Mel-Rir have not 

 yet been surveyed in all directions ; but M. Roudaire has con- 

 cluded from various observations that the mtan depth of the 

 two Chotts Mel-Rir and Rharsa must not be below 24 metres. 

 The small Chott El Asloudj, which is intermediate, has a mean 

 depth of only from one to two metres, which makes him regard 

 it as a slightly elevated barrier between the two great lakes. If 

 it be admitted that this barrier could be pierced by a trench of 

 suitable depth, and that the water of the sea were led from the 

 Gulf of Gabes to the entrance of the Chott Rharsa, the sea 

 would fill that chott, .is also the Chott Mel-Rir, and the depth 

 of water would be sufficient in the two lakes for the navigation 

 of all vessels. Articles of commerce could be transported thence 

 to all parts of the world without any re-embarkation. 



Such is the starting-point of a project for an inland sea which 

 M. Roudaire has had constantly in his mind during all his 

 labours : he is confident that the execution is an easy matter, 

 without allowing himself to be discouraged by any obstacle. 

 The enterprise, supposing it to be realised, would certainly not 

 piesent commercial advantages comparable in any respect to 

 those resiUting from the canalisation of the Isthmus of Suez. 

 The products of Central Africa, transported by camels across 

 the desert do not seem to be sufficiently abundant to furnish 

 freight for a large number of vessels. There is no doubt, how- 

 ever, that if the products of Central Africa had no longer to 

 bear the expense of so long a carriage by land, their price would 

 be notably lowered and their consumption increased. But 

 indeed it would be impossible to estimate the benefits which in 

 the future would result from the creation of such an inland sea. 

 Considerations of another kind leave no doubt, M. Fave thinks, 

 as to the improvements which would result from an inland sea 

 covering 13,230 square kilometres, from a climalic point of view 

 and in relation to the fertility of the soil. 



Prof. Tyndall was engaged for some years in determining the 

 action which the vapour of waler exercises upon radiant heat. 

 He has proved that even with complete transparency to light, 

 the vapour of waler absorbs radiant heat to a very notable extent. 

 The vapour of water possesses that absorbent property much 

 more than the air with which it is mixed, in however small a 

 proportion ; and its absorbent power increases very nearly in 

 proportion to its mass. Prof Tyndall has not failed to bring; 

 out the influence which the invisible vapour of water contained 

 in the air exercises upon temperature, both during day and 

 night, and he has been able hence to draw immediate conclu- 

 sions as to its influence upon the life of plant-. After having 

 measured directly the quantity of heat absorbed by very minute 

 quantities of vapour of waler mixed with air in his experimental 

 tubes, he feels authorised to speak thus: — "Considering the 

 earth as a source of heat, it may be admitted as certain that at 

 least 10 per cent, of the heat which it tends to radiate into space 

 is intercepted by the first six feet of moist air which surrounds 

 its surface." Prof. Tyndall hence draws this conclusion : — 

 "The suppression, during a single night of summer, of the 

 moisture contained in the atmosphere which covers England 

 would be accompanied by the destruction of all the plants 

 which frost kills." 



It is not only the cold of night which is increased at the 

 surface of the ground by the dryness of the air, but also the heat 

 of day ; so that the variations of temperature produced in 

 twenty-four hours are sometimes very great and very prejudicial 

 to the vegetation of a great number ot plants. We miy apply 

 these considerations to the region of the chotts, where M. 

 Roudaire, in his expedition of 1S74-5, found heat of 25° (C.) 

 during the day, and cold of S^ below zero during the night. 

 After that we need not be longer surprised that the lands 

 comprised between the slopes south of Aures and the chotts 

 produce very little, however favourable in themselves they may 

 be to vegetation. If we admit with M. Roudaire, agreeing in 

 this point with all explorers cf the chotts, that their cavities have 

 at one time formed salt lakes, dried up gradually during the 

 historic period, we shall obtain an explanation of the changes in 

 the production of the soil of the jirovince of Constantine, and of 

 Tunis since the epoch of Roman domination, when the province 

 of Africa was much more populous and much more fertile than at 

 present. 



M. Roudaire has sought to find results of observations from 

 which he might conclude what would be the depth of the bed of 



