354 



NATURE 



\_Augtist 23, 1877 



water evaporated after the creation of the inland sea. He has 

 found this information in the experiments made at the Bitter 

 Lakes traversed by the Suez Canal. At the time of the filling- 

 up of the Bitter Lakes, a waste-weir was constructed intended to 

 regulate the introduction of the w.ater of the Mediterranean. 

 From July 7 to 14 the weir was wrought with only a small 

 number of sluices raised, and the level of the lakes remained 

 stationary. The introduction had been regulated to about 

 3,540,942 cubic metres, or, in round numbers, 4,000,000, cubic 

 metres per day. This figure, then, gives the quantity of water 

 absorbed by evaporation which, according to the extent of 

 surlace, produced a lowering of the level of from 'ooj m. to 

 •0035 m. during twenty-four hours, and that in the hottest month 

 of the year. All the observations mjde since that time have 

 given essentially the same results, and we must admit, with the 

 engineers of the Saez Company, a general mean bf '003 m. per 

 day, or i m. per year. M. Roudaire has added, as a conclusion 

 to be drawn from this bearing on his project : — " The ba-in of 

 the chotts and the Isthmus of Suez being situated nearly under 

 the same latitude, and possessing a climate absolutely analogous, 

 we must admit that the evaporation which will be produced on 

 the inland sea will be the same as that which has been observed 

 on the Bitter Lakes. The figure '003 m. is the general mean 

 of the year. The obs'ervations which we have made in the 

 chotts with Piche's evaporometer have proved to us that this 

 figure is at least d^jubled during the sirocco." 



Not only would the vapour of wa'er thus diffused through the 

 air serve as a reservoir for the heat emanating from the earth or 

 the sun, but it would have still another mode of action for 

 effecting climatic modifications. The air and its vapour brought 

 into contact with the elevated and therefore cool parts, the 

 Aures mountains, and other mountains of Algeria, would, have 

 their temperature lowered on account of that cau^e, and the 

 effect would be increased by the radiation of the vapour of water 

 into space ; for that radiation would operate almost without 

 check at a height where the air from above, and therefore less 

 dense, is cold and dry. Under the influence of this double 

 cause the moisture would be condensed into rain or snow, and 

 would serve to feed the watercourses which would permanently 

 flow in the beds at present dry during a great part of the year. 

 We should see issuing from the ground, from the same cause, 

 sources which do not now exist. The moisture, discharging 

 itself along the lines of watercourses, would extend its influence 

 on the two slopes of the mountains to countries at a distance 

 from the chotts. We can perceive by calculations the volume 

 and the weight of the masses of water set in motion by evapora- 

 tion, that these considerations are not chimerical. The 13,230 

 square kilometres give 39,690,000,000 kilogrammes of water per 

 twenty-four hour.*, raised by evapor.rtion, /.(■., 39,690,000 cubic 

 metres. It will be seen that there is here something to form 

 sources and feed streams or rivers. M. Roudaire has calculated 

 that the quantity of vapour diffused in air who>e barometric 

 pressure is 760 m., and the temperature 12- C, would cover the 

 surface of Tunis and Algeria with a layer of half-.saturated air, 

 24 metres in height. Let us remark that this calculation includes 

 only the quantity of vapour formed during twenty-four hours. 

 The south wind known as the sirocco, at present so destructive 

 because it is exceedingly dry, would produce on the surface of 

 the lakes an evaporation much greater than that mean, and 

 would, moreover, lose many of its hurtful effects. In fact, this 

 same wind, which destroys the vegetation of Algeria, has a 

 fertilising influence on the territory of France, because of 

 the moisture with which it becomes charged in crossing the 

 Mediterranean. 



Advantages so considerable, which would result from the 

 introduction of the water of the sea into the chotts, explain and 

 justify the perseverance with which M. Roudaire has pursued the 

 idea without allowing himself to be arrested by any of the diffi- 

 culties which have presented themselves. The greatest of the 

 difficulties, M. Fave thinks, proceeds from the fact that the 

 Chott El-Djerid, the nearest to the Gulf of Gabes, has not, like 

 the others, the bottom of its basin below, but above, the level 

 of the sea. The surface of the ground is undulating ; it rises 

 to 20 metres, or even more, at certain points, and descends to 

 zero at other points. M. Roudaire has estimated, somewhat 

 vaguely, that the mean height of the bottom may be about 

 6 metres above sea-level. Notwithstanding this obstacle, M. 

 Roudaire does not renounce the hope of being able to make the 

 water of the sea reach the Chott El-Djerid in order to turn it 

 afterwards into the other two chotts. He believes he has founil 

 a support for this In the nature of the bottom, or, to speak more 



exactly, in the existence of a water-bearing bed situated at a 

 small depth below the ground. 



The Commission, of which M. Fave is the mouthpiece, with- 

 out pronouncing definitely on the project of M. Roudaire, 

 s ifficient data for this not being forthcoming, strongly recom- 

 mend that active steps be taken to obtain more accurate 

 measurements and other data. The facts which he has addaced 

 they think sufficient to justify serious attention being pa'd to his 

 proposal, and recommend that the thanks of the Academy be 

 accorded to M. Roudaire for his valuable labours. To these 

 recommendations the Academy agreed. 



We should state, however, that MM. Dumas and Daubree, 

 members of the Commission, are not able to give their entire 

 consent to the recommendition of M. Fave's report. They 

 think that the obstacles to the accomplishment of the scheme 

 are much more serious thin have been estimated, and regard 

 the industrial and climatic results anticipated as, to a considerable 

 extent, hyp ithetical. M. de Lesseps, however, gives his entire 

 concurrence to the scheme of M. Roudaire, and believes in its 

 practicability and the favourable results that would follow its 

 realisation. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



Science AND ARTDEPARTMENT.^The Committee of Council 

 on Education have just issued an important circular on instruc- 

 tion in practical chemistry and in physics. My Lords direct 

 that S§ XLV. and Lxxi. of the Science Directory be cancelled 

 and that the following rules be substituted: — I. Payments of 

 i/. loj. and i/. for the first and second class in the elementary 

 stage, and of 4/. and 3/. for the first and second class in the 

 advanced stage and honours, will be made on the results of in- 

 struction in practical chemistry. They will be claimable accord- 

 ing to the same rules, and subject to the same deductions on 

 account of previous success as the ordinary payments. These 

 payments will be made on condition — (a) That there be a good 

 laboratory — being a room, or part of a room, exclusively devoted 

 to the purpose of the study of practical chemistry — properly fitted 

 with gas and water supply, (b) That the student on wliom the 

 payment be claimed have received twenty-five lessons at least in 

 laboratory practice since his last examination, each lesson being 

 an attendance of at least one hour and a half's duration on a 

 separate day. (c) That a register of the attendance of the 

 students at the instruction in practical chemistry be kept duly 

 posted up from day to day. 2. Elementary S/age. — In this stage 

 the knowledge of the students will be tested by special questions 

 set with the ordinary examination paper ; but no payments will 

 be made if the laboratory be not furnished with all the apparatus 

 necessary for the individual practice of each student in practical 

 chemistry, and if systematic instruction in practical chemistry be 

 not given. Any student on whom it is intended to claim pay- 

 menis in this stage may be called on by the Inspector of the 

 Department, when visiting the laboratory, to repeat some of the 

 experiments, specified in the Science Directory in the syllabus 

 for the first stage of inorganic chemistry, which he has had an 

 opportunity of witnessing. 3. AiivanceJ Stoge ami Honours. — 

 The results of the instruction in these stages will be tested by a 

 special examination in qualitative analysis to be held on a Saturda •■ 

 during the ordinary May examinations, and lasting, for the 

 advanced stage from 6 p.m. to 10 p.m., and for honours from 

 2 P.M. to 10 P.M. Payments can only be claimed in these stages 

 provided — (<7) That the laboratory be fitted up with a separate 

 working place for each student. (/') That each student be pro- 

 vided with a complete set of apparatus and chemical tests (as 

 enumerated in Science Form No. 402) kept separate, and in 

 good working order, on the shelves, and in the cupboard or 

 drawers at his own tab e. (c) That the laboratiiry be also fur- 

 nished with apparatus for general use, consisting of at least the 

 articles of which a list will be found on Science Form No. 402. 

 From the reports of the examiners and of the inspectors it appears 

 that instruction still continues to be given in physics without a 

 sufficient amount of apparatus to illustrate the teaching of these 

 experimentai sciences. My Lords cannot allow examinations to 

 be held in schools where instructions of such a superficial and 

 perfunctory nature is given. They therefore direct that in 1878 

 no classes be examined which are not furnished with apparatus 

 at least sufficient to illustrate some of the more important experi- 

 ments ; which apparatus the teacher may be called upon by the 

 Inspector of the Department to show his ability to use. 



