June 1, 1867.] 



HAEDWICKE'S SCIENCE-GOSSIP. 



139 



strange to be met with in various parts of Lower 

 Egypt— as, for instance, the existence of sea-water 

 shells in different portions of the desert, and above 

 all the petrified desert— it is evident that the whole 

 of this part of the country was at one time covered 

 by the sea. The Mokattam mountains are of a light 

 yellow colour ; the summits are quite free of any sort 

 of vegetation, and various parts are covered with loose 

 blocks of stones of the calcium species. There is 

 in these mountains a very remarkable rock of a 

 reddish colour, called by the Arabs Ghebel Achmar, 

 which means literally red mountain. It is of a 

 very soft nature, and closely resembles red ochre. 

 In this range there are also immense caves, in each 

 of which a regiment of soldiers might easily be 

 quartered. The whole of Upper Egypt might be 

 said to be a vast mass of granite, but Lower Egypt, 

 at all events the Delta, having been probably formed 

 by the clay and sand brought down by the Nile, 

 shows no visible traces of this rock. The centre of 

 the earth is a vast crucible in which materials of 

 which we have no precise knowledge are fused or 

 melted together, and then forced up to the surface, 

 either by the intense heat or by a sort of centri- 

 fugal force. The composition called granite is formed 

 and forced upwards in this manner, and as it cools 

 and hardens bursts its way through the softer strata 

 until it appears above the surface, assuming in many 

 places the forms of stupendous mountains. Some- 

 times the force is only sufficient to raise the strata 

 above to a certain height, while the granite itself 

 remains concealed underneath. This may account 

 for aqueous deposits being found in the shape of 

 mountains, as in the instance of the Mokattam 

 mountains in question. They once probably formed 

 the bed of the ocean, and in the course of ages were 

 raised to their present height by the upheaving of 

 igneous rocks from below. — E. St. John Fairman. 



Age of Niagara. — Many eminent geologists 

 affirm that the eroding power of the swift rolling 

 waters of the Columbia, Potomac, and Missouri 

 could not, on an average, effect the stupendous 

 erosions alluded to in less than 40,000 years ; and 

 Sir Charles Lyell asserts, after personal study, and 

 close searching and accurate observation of the 

 nature and properties of the Silurian rocks of the 

 Niagara bed, and of the average annual rate of the 

 erosion at present, that the strength of the eroding 

 power, great though it be, could not possibly have 

 effected the retreat of the cataract to its modern 

 site in less than 35,000 years. — The Twin Records of 

 Creation. 



Eossil Dormouse. — At the meeting of the 

 Zoological Society of London, 9th May, Dr. A. 

 Leith Adams read a communication respecting a 

 new fossil Dormouse from the quarternary forma- 

 tions of Malta, proposed to be called Myoxus 

 melitensis. 



MICROSCOPY. 



Feathers for Mounting.— The feathers from 

 the drake's head form a very interesting object 

 under the microscope. Under a power of 80 dia- 

 meters they appear to be divided into rectangular 

 cells. Their colour, when viewed opaque, is beau- 

 tiful. Can any one tell me if there is mention of 

 them in any work on the microscope ? The cells 

 are best shown when mounted in balsam.—^. W. 

 Cooper. 



Centering Objects. — As hardly any hint in 

 microscopic manipulation is too trifling to be of 

 use, at least to beginners, I venture to send the fol- 

 lowing device, which I have used for some years, as 

 from the exce?itric position which objects sometimes 

 occupy on the slide it is evident that some mounters 

 trust (vain confidence !) to the eye alone. Cut a 

 piece of card the exact size of a slide, draw two 

 lines diagonally from corner to corner, the point of 

 intersection will show the centre, where a small hole 

 should be punched or cut out. To use the con- 

 trivance, place it carefully on a slide, and with a 

 pen put a dot of ink on the glass through the hole ; 

 the object is of course to be mounted on the other 

 side of the slide, and the ink-spot is easily scraped 

 off afterwards. The dot on the glass is preferable 

 to any loose mark placed underneath while mount- 

 ing, as it cannot possibly shift its position. — George 

 Guyon. 



Mounting Objects. — As I continually see in 

 Science-Gossif discussions on the relative merits 

 of various fluids for mounting microscopic objects, 

 I would say a word on behalf of a very simple 

 one, viz., distilled water. I have now lying before 

 me on my table two specimens which were among 

 my earliest attempts at mounting, and which were 

 mounted at least eighteen years ago. Out of these 

 eighteen years they have passed more than fourteen 

 with me in the tropics, and yet they are as green 

 and as fresh, and as perfect for microscopic examina- 

 tion as they were on the day they were mounted. 

 The objects are Nostoc vulgare and Jungermannia 

 tomentetla. They are both mounted on slips of glass 

 of the usual size, viz., 3 inches by 1. In one case 

 the cell in which the object lies was built up of red 

 sealing-wax dissolved in spirits of wine, and the 

 thin glass cover cemented with the same. As the 

 sealing-wax was laid on in a broad band (nearly 

 three-tenths of an inch) no air at all has got in, and 

 the specimen is in every respect as perfect as it was 

 eighteen years ago. This is the more surprising as 

 sticks of the very same sealing-wax brought out to 

 : this country, and laid in a drawer, in consequence 

 ; of the heat, soon ran together, and flowed out into a 

 ' flat circular cake. The effect of dissolving it in 

 spirits of wine seems to have been to enable the wax 



