68 



SCIENTIFIC NEV/S. 



[Jan. 20, I? 



graph have already been made at Marsden, and seven 

 months' results are given in the paper. An interesting 

 feature in the records is the irregular and perturbed 

 movements which lasted from February 7th to March 

 I2th, 1887, and which appear to be connected with 

 disturbances originating at places far distant from the 

 observatory at Marsden ; and it is considered probable 

 that the shocks experienced at St. Louis, in the United 

 States, on February 7th, were more violent results of the 

 motions recorded here on the same day. These motions 

 continued until February 23rd, the date of the disturb- 

 ances at Nice and adjacent district, and ceased on March 

 1 2th, when the series of Italian disturbances were over. 

 The shocks recorded on March 14th seem to have been 

 reverberations of those experienced in Bohemia and 

 Burmah. These experiments have been made with 

 somewhat rough apparatus, but will shortly be extended 

 with the aid of a more perfect form of seismograph, 

 made from the designs of Professor Ewing, of the Uni- 

 versity College, Dundee, and the continued observations 

 will be accompanied by the measurements of the per- 

 centage of gas found in the return air of the mine, which 

 will be made by some of the best apparatus for such 

 purposes. The measurements of the proportions of gas 

 have not been made up to the present time, but it may 

 be mentioned as at least a curious coincidence that the 

 disturbances of December 6th and 8th were closely 

 followed by increased issues of gas at several of the 

 collieries in this district. 



Professor Lebour said the British Association, at its 

 meeting held at Manchester, after considering the work 

 that had been done by the Earth Tremors Committee of 

 this Institute, had thought it desirable that the observa- 

 tions should be extended over a greater part of the coun- 

 try ; and the British Association appointed an influential 

 committee to consider the advisability and possibility of 

 establishing a network of seismological observations over 

 England. The British Association committee were to 

 consider whether the work as done by this Institute was 

 to be imitated or not. Sunderland was the locality which 

 first called the Institute's attention to these earth tremors. 

 Mr. James M'Kinless described " A Gauzeless Safety 

 Lamp." This is a species of lamp like the Mueseler, in 

 which the flame is surrounded with a glass cylinder, 

 but, unlike the Mueseler, it has no gauze. The air is 

 admitted above the flame by means of very small holes 

 drilled through a brass ring about ^ of an inch thick, 

 each hole forming a kind of tube of considerable length 

 as compared with its diameter ; thus the heat-absorbing 

 surface is very great. A similar mode is employed to 

 allow the heated air to escape. An internal cone or 

 chimney is so arranged as to protect the glass at the top 

 from the action of the flame should the lamp be tilted. 



Mr. Emerson Bainbridge also described " A Miner's 

 Safety Lamp designed to meet the Requirements of the 

 Mines Regulation Act which came into force on January 

 1st." The lamp is composed of only four movable parts, 

 which are simple and easily put together. By a simple 

 shut-oft'arrangement the inlet of air which supports com- 

 bustion can at once be closed if the presence of gas is 

 discovered. 



BOURNEMOUTH SOCIETY OF NATURAL 



SCIENCE. 



Mr. C. Carus- Wilson, F.G.S., delivered a lecture on 



" Grains of Sand," in which he pointed out that sand is 



a product ol the disintegration and subsequent attrition of 



granitic or siliceous rocks. Granite is composed of three 

 minerals, quartz, mica, and felspar. Of these felspar is 

 the first to decompose, containing in its composition silicate 

 of alumina, which absorbs water, and becomes a hydrated 

 silicate of alumina. It then crystallizes and forms the 

 basis of all clays. The felspar being thus decomposed, 

 granite becomes a soft plastic rock, so soft, indeed, that it 

 can be cut with a knife as clay. In this way the con- 

 stituents of granite are washed away by the action of 

 water, the felspar to form clay, the mica micaceous slates, 

 and the quartz granules the sands and sandstones. Quartz 

 is one of the hardest minerals ; its degree of hardness is 

 seven in the scale, thus being only three behind the 

 diamond, the hardest substance known. It is composed 

 of oxygen and silicon, and crystallizes in the hexagonal 

 system, commonly known as the six-sided prism. The 

 lecturer showed that grains of sand might be angular, 

 sub-angular, rounded, spindle-shaped, or cylindrical and 

 occasionally hexagonal prisms. The shape was seen to 

 depend largely on the forces that had been at work on 

 them. Thus, blown sand was usually composed of 

 rounded grains, owing to the amount of friction they had 

 undergone. The colour of sand varies from pure white 

 to_deep black,depending on the kind and amount of mineral 

 matter with which the grains were associated or 

 surrounded. Sands were shewn to be generally coloured 

 externally, as those coloured throughout, such as amethyst, 

 cairngorm, or jasper were extremely rare. Attention was 

 drawn to the various agencies of rivers and streams, by 

 which sand is transported to lakes and seas, there to form 

 deposits which, in their turn, will probably become rocks, 

 and may in future ages be disintegrated again. To show 

 the vastness of these agencies it was mentioned that the 

 Mississipi annually carries down to the sea seven hundred 

 and fifty million cubic feet of sand, gravel, and vegetable 

 matter, a quantity sufficient to form a solid mass nearly 

 a mile square, and two hundred and seventy feet high. 

 When the sand has been deposited in lakes and seas it 

 has only to become compact and coherent to form sand- 

 stones. As a rule some mineral matter, such as iron 

 silica, or lime was deposited round the grains, so forming 

 a cement which subsequently binds them together. The 

 most durable sandstones are those in which the grains are 

 united together by a siliceous cement, the most notable 

 examples of this class being the Agglestone Rock at Stud- 

 land, and the masses at Stonehenge, which are known as 

 sarsees. Nearly all sandstone is porous and admits the 

 free percolation of water, the carbonic acid it contains dis- 

 solving the mineral cements. Attention was called to the 

 commercial and domestic uses of sand in building and glass 

 manufacture. The lecturer also pointed out the immense 

 effect sand had upon the climate and scenic features of 

 any neighbourhood. Sandy soils are dry and absorbent 

 and do not promote much humidity in the atmosphere ; 

 they receive and part with heat more quickly than any 

 other soils. This is well seen in parts of the great desert of 

 Sahara, where the temperature reaches 150° F. in the day- 

 time and falls to 20° F. at night. 



•H>!^»S5^^■ 



Photography under Water. — The French Ministry 

 of Marine has adopted an invention by which photo- 

 graphs of vessels sunk in deep water may be taken. 

 This is effected by means of a camera worked by an elec- 

 tric incandescent light, and it is fully expected that the in- 

 vention will also make the operaUon 01 divers much easier. 



