December ii, 1891.] 



SCIENCE. 



3*5 



It is difiScult to explain tbis phenomenon except upon the 

 theory that this incrustation is the deposit accumulated upon 

 these low plains in the course of centuries upon centuries, 

 daring which the annual meltiiig of the snows upon the 

 mountains and highlands, besides the rainfall and the peren- 

 nial streams which drain into this basin, have brought down 

 in the water from the strata of salt through which they pass 

 these tremendous quantities of salt in solution. The summer 

 sun has dried up the water by evaporation and left the salt 

 deposit lying upon a soil more or less saturated with mois- 

 ture, this layer of salt thus deposited has gained in thickness 

 and consistency year by year until it has become a solid ho- 

 mogeneous mass too 6rmly bound together in the parts dis- 

 tant from the edge, where its thickness was most (owing to 

 the greater depth of water which accumulated there, and 

 consequent larger amount of salt deposited), to be broken by 

 any pressure of water from below. The perennial streams 

 have thus poured their waters underneath this strata, as the 

 accumulation of water would naturally commence at the 

 lowest part of the hollow, which would be about the middle 

 of the salt plain, while the floods of water brought down by 

 the rain and melting snow would overflow on to its surface 

 from the margins. This is the only way by which it oc- 

 curred to us that we could account for the dead level of the 

 crust which, though covering a space of ground more or less 

 hollow in its nature, as was evident from the run of the 

 water all around, did not appear to us to slope in any direc- 

 tion, and also for the fact that on piercing through this crust 

 water spouted out from below. Though we had no ocular 

 demonstration of this fact, we were satisfied that it was the 

 case from the accounts of a party of our servants whom we 

 sent out the following day, when we had reached the further 

 edge, to bring us a block of salt at a distance of a mile or 

 two from the shore; another fact in support of this theory 

 was that nearer the edge, where the crust was thinner and 

 thus unable to resist the pressure from below, it had evi- 

 dently been burst by the rising of the water during the win- 

 ter and spring, and lay tossed about in fragments. 



After this halt we continued our march and arrived at the 

 farther margin about 3 A.M. ; it had thus taken us a good 

 eight hours to cross this plain of salt, so that the distance 

 traversed could not have been less than about twenty miles. 

 As we expected, wo found that, as we approached the farther 

 side, the crust of salt got thinner and thinner, till, on one 

 occasion, getting slightly off the track, we quickly found the 

 horses and mules sink through it almost up to the girths in 

 a substance that resembled exactly melting snow, out of 

 which we had to make the best of our way towards the 

 harder material upon which we had been marching for so 

 many houi-s. At length we hit off the beaten track which 

 had been hardened by constant use during so many centu- 

 ries, and were thankful indeed when we found ourselves 

 again at last on terra flrma. 



NOTES AND NEWS. 



At the Franklin Institute, Philadelphia, on Friday evening, 

 Dec. 11, a lecture was delivered by Mr. William L. Saunders, the 

 well-known civil engineer of New York, on "The Compressed Air 

 Power of the Future." 



— During the summer the third and fourth stories of the south 

 wing of University Hall, Ann Arbor, were fitted up as zoological 

 and botanical laboratories. Each story affords about four thousand 

 square feet of floor space. Ou each floor there are three principal 

 rooms: a central room about forty-five feet square, a north room 

 about twenty by forty feet, and a south room of the same size. 

 There are also small rooms for the use of instructors. The fourth 



floor is devoted to botany, the central room being uecd as a gen- 

 eral laboratory, the north room as a herbarium, and the south 

 room as a research-laboratory for advanced students A small 

 conservatory is to be constructed against one of the windows of 

 the south room and wiD serve for experimental work. The other 

 south window is occupied by an equarium. The third floor is de- 

 voted to zoology, the middle room being used as a general labora- 

 tory for beginners, and the north room for advanced work in 

 vertebrate morphology. The south room has been divided into 

 three compartments. One of these is lined with galvanized iron 

 and serves to house the small animals required in the daily work 

 of the laboratory. The second is used for alcoholic epecimensy 

 and the third is fitted up as a private laboratory for the professor 

 in charge. In the zoological laboratories particular attention has 

 been paid to the provision of means for keeping alive the animals 

 that inhabit our inland waters. There are four large aquaria, and 

 provision has been made for thirty-six smaller ones. There are 

 also cages with running water for crayfish, frogs and other small 

 animals that do not thrive weU in ordinary aquaria. Each of 

 these laboratories, the botanical and the zoological, can accom- 

 modate about fifty students. Contrary to expectation, they are 

 now filled to nearly their full capacity, and by another year are 

 likely to be crowded. 



— Special Agent C. J. Murphy, charged with the introduction 

 of Indian com as a human food into Europe, has made a report 

 to Secretary Rusk covering his work in Great Britain. In it he 

 reviews the conditions which seem likely to encourage the use of 

 this cereal food in Great Britain and other parts of Europe, and 

 points out the various channels through which he has sought to 

 introduce it, and the necessity for the co-operation of private in- 

 dividuals and commercial bodies in this country to take advantage 

 of the work already done by the Government in this direction. 

 Secretary Rusk has caused to be prepared for publication, in con- 

 junction with Special Agent Murphy's report, a chapter upon the 

 value of maize as food, by Dr. H. W. Wiley, chief chemist of the 

 department, in which are shown the chemical composition of 

 maize and its relative value for food purposes by comparison 

 with other cereals. There is also a chapter, prepared by the as- 

 sistant statistician, Mr. B. W. Snow, under the direction of the 

 statistician, offering some additional observations as to the possi- 

 bility of extending the use of this cereal among the people of 

 Europe as a human food, and presenting a number of statistical 

 tables showing the yield and value of our com crop and the ex- 

 tent of our available resources in supplying home and foreign de- 

 mand. The report is now in press and will be shortly ready for 

 distribution. 



— In a recent paper on the camel (Zeits. fur wissen. Geogr.) 

 Herr Lehmann refers, among other things, to its relations to tem- 

 perature and moisture. Neither the most broiling heat, nor the 

 most intense cold, nor extreme daily or yearly variations, accord- 

 ing to an abstract in Nature, hinder the distribution of the camel. 

 It seems, indeed, that the dromedary of the Sahara has better 

 health there than in more equably warm regions; though, after a 

 day of tropical heat, the thermometer sometimes goes down sev- 

 eral degrees below freezing, and daily variations of 33.7° C. occur. 

 In Semipalatinsk again, where the camel is found, tie annual va- 

 liation of temperature sometimes reaches 87.8°. In Eastern Asia, 

 winter is the time the animals are made to work. In very intense 

 cold, they are sewn up in felt covers. Of course each race of 

 camel does best in the temperature conditions of its home: a Sou- 

 dan camel would not flourish in North-east Asia. Camels are 

 very sensitive to moisture. In the region of tropical rains they 

 are usually absent, and if they come into such with caravans, the 

 results of the rainy season are greatly feared. The great humidity 

 of the air explains the absence of the camel from the northern 

 slopes of the Atlas, and from well-wooded Abyssinia. This sen- 

 sitiveness expresses itself in the character of different races. The 

 finest, most noble-looking camels, with short silk- like hair, 

 are found in the interior of deserts (as in the Tuarek region, in 

 North Africa), and they cannot be used for journeys to moist re- 

 gions. Even in Fezzan (south of Tripoli) the animals are shorter 

 and fatter, with long coaree hair; and in Nile lands, and on 



