476 



SCIENTIFIC NE^A^S. 



[May i8, l8 



formation of many a perpendicular cliif could, he argued, 

 be easily explained if the true denudant — wind — was 

 given its proper rank as one of the sculptors of the 

 earth's surface. Moisture and heat disintegrated the rock 

 face of the cliff, while wind carried particles miles away, 

 not only to lower but also to higher levels. Many fine 

 sands above a cliff that were supposed to have come 

 from a higher level had come from below, having been 

 carried by the upward eddy curling up over the cliff 

 edge, to be deposited in its shelter. Moreover, wind did 

 not confine itself to the driftage of fine particles, as it was 

 also capable of moving pebbles and stones of a fair size 

 if they were flat and more or less disc-shaped. Wind 

 not only acted as a direct denudant, but it also generated 

 " sand blasts." This was so conspicuous in cities such 

 as New York as to induce public attention. It might also 

 be observed at home, at street corners and other places 

 round which the wind swept, the lower stones being 

 gradually worn away. The under-cut stones at different 

 heights on a hillside puzzled those who beheved that 

 water was the only agent capable of under-cutting ; while 

 if winds were allowed to be the agent they were easily 

 understood. Mr. Hugh Miller exhibited a collection of 

 pebbles polished by drifting sand, from the deserts of 

 Upper Egypt and Nubia near the first cataract of the 

 Nile. Speaking of under-cut stones dealt with in the 

 previous paper, he said it had been contended that the 

 Sphinx was in all probability a stone that had had its 

 base swept by the wind until it had a more or less animal 

 form, and that the upper part had been sculptured, very 

 little trouble being required in hollowing out the neck. 



DUNDEE NATURALISTS' SOCIETY. 

 At a meeting of the physical section, held on May 2nd, 

 Professor Ewing (President), who occupied the chair, 

 described and exhibited an apparatus for testing seismo- 

 meters or earthquake recorders, by means of which the 

 degree of accuracy was determined with which the seis- 

 mometer responded to and registered the motion of the 

 ground during an earthquake. The apparatus consisted 

 of a lever pivoted by a gimbal joint to a bracket which 

 was fixed to the frame of the seismograph, while the 

 short end of the lever was prevented from moving by 

 means of an independent support. The seismograph was 

 set up on a board mounted on rollers so that it could be 

 made to move about as if an earthquake were in progress. 

 Its own recording lever and the independent lever then 

 traced out, side by side, two diagrams of the motion, and 

 the agreement of these diagrams with one another 

 furnished proof of the accuracy of the instrument. Pro- 

 fessor Ewing mentioned that he had been in the habit of 

 using this test since the first construction of his seismo- 

 graph seven years ago. He exhibited the apparatus in 

 action, and also submitted a large number of pairs of 

 diagrams taken by it. Professor Carnelley then read 

 a paper by Mr. John Alexander and himself on " The 

 Colour of some Carbon Compounds," in which he gave 

 an account of experiments they had recently made as to 

 the circumstances which condition the colour of such 

 compounds, dealing more especially with the effect of 

 temperature, atomic weight, atomic arrangement, and 

 amount of water of crystallisation. Professor Carnelley 

 finally read a paper on the influence of atomic weight 

 and atomic arrangement on the amount of water con- 

 tained in the crystals of metallic salts of both organic 

 and inorganic acids. 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents, nor can he take notice of anony?noics com- 

 munications. All letters must be accompanied by the name and 

 address of the writer, not necessarily for publication, but as a 

 guarantee of good faith. 



RED SNOW. 

 The subject ot red snow having been mentioned more 

 than once in your columns, I send you a drawing of the 

 deposit I obtained from a large patch of red snow which 

 I found in Switzerland in August, 1877. Durmg the ascent 

 of the Schilthorn I came across a patch of snow about 

 fifteen to twentv feet long by six to twelve feet m width, 

 forming apparently part of the rest of the snow which 

 covered that part of the mountain. I cannot remember the 

 depth to which the colour penetrated, but there was no diffi- 

 culty in collecting a quantity, and 1 think that it must there- 

 fore have been at least half an inch deep. Underneath was 

 a considerable depth of ordinary snow. The colour may be 

 imagined when I say that it appeared at first to have been 

 stained deeply with blood. I emptied a pocket flask, and 

 cleaned it as well as I could by shaking clean snow in it. I 

 then filled it with red snow. On returning to the hotel, the 



TTuruScuiiiihs of cin Inch,. 



snow had of course melted, and the liquid, which now 

 measured about half an ounce, was of a muddy reddish 

 brown colour. After allowing it to settle, a quantity of the 

 sediment was deposited. The water above was practically 

 clear. I Ipoured this away, having no microscope at hand, 

 and added to the sediment an equal bulk of the best glycerine 

 which I could obtain at Lauterbrunnen, together with two or 

 three drops of carbolic acid. A month or two after, on 

 returning to England, and not having my mounting materials 

 at hand, I took the bottle to Mr. Pillischer, of Bond-street, who 

 mounted several slides. I afterwards mounted about half a 

 dozen myself, and gave them away. Of the two which I 

 have left, both having been prepared by Mr. Pillischer, one 

 only has survived, the other having been attacked by a 

 thread-like grovvth. The colour has almost entirely dis- 

 appeared, but the general appearance remains the same. 

 The sediment consists almost entirely of the separate cells 

 of Protococcus Nivalis. This is very similar to the green 

 plant which colours the stems of trees or old palings. One 

 feature has apparently been lost or obscured during the ten 

 years that it has been in my cabinet. Some of the largest 

 cells at one time showed signs ot internal division into three 

 to five parts, but I could never satisfy myself that these con- 

 tained separate nuclei. I believe the mode of propagation of 

 this plant is rather uncertain. I send you the specimen for 

 examination. 



There are a few yellowish scales, or shells, whose nature 

 I never could determine. There are hardly any other foreign 

 substances, except in this particular specimen, which con- 

 tains another yellowish flake with a well-marked pattern 

 on it, and which evidently formed part of some large struc- 

 ture. The other scales give me the impression of having 

 been the complete shells of some animal. A. P. T. 



BRITISH LICHENS. 

 I should feel much obliged if any of your readers could tell 

 me of a book on British Lichens, written in a popular manner. 



