n8 



SCIENTIFIC NEWS. 



[Aug 3l 1888. 



covered with another specimen which fills up all the 

 interstices between the previously formed mineral, an 

 incontestable proof of the priority of the crystal. With 

 the aid of these convincing facts, chronological lists have 

 been obtained showing the state of crystallisation of 

 each species of the two great periods. We have not 

 space to quote them here, but we get glimpses of the law, 

 discovered by synthetical experiments, which governs 

 the formation and the relative ages of crystals. We 

 have only drawn the outline of the history of lava ; but, 

 although we have been unable to do more than sketch in 

 certain of the details of this representation of lithological 

 phenomena, which modern investigations have delineated 

 with such startling fidelity, we have indicated enough to 

 amply and forcibly prove the great capabilities of analysis 

 as a coadjutor of thoughtful reasoning. From this stand- 

 point the study of lava, such as we are endeavouring to 

 interpret, presents surely one of the finest possible 

 examples of the application of inductive methods to 

 natural sciences. We scarcely know what to admire 

 most, the process of analytical operations, the skill of the 

 observers, or the logical chain of thought by which the 

 phenomena are connected. By this powerful mode of in- 

 vestigation, microscopical analysis, we are enabled to 

 trace with minute exactitude the process of crystallisa- 

 tion in a rocky mass where the naked eye fails to detect 

 anything but an indistinct uniformity, to penetrate into 

 this wonderful tissue of volcanic products, which contain 

 millions of polyhedrons in a cubic centimetre, to determine 

 with mathematical precision the nature of each of these 

 infinitesimal bodies, to follow them from their origin 

 through their entire development, and to mark the traces 

 of all their modifications by chemical and physical 

 agents. 



(7b be continued.) 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents, nor can he take notice of anonymous 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. 



RECENT INVENTIONS. 



7he following list has been compiled especially for the Scientific 

 News by Messrs. W. P. Thompson and Boult, Patent Agents, of 

 323, High Holborn, London, IV. C. ; Newcastle Chambers, Angel 

 Row, Nottingham; Ducie Buildings, Bank Street, Manchester; 

 and 6, Lord Street, Liverpool. 



A CIRCLE PROBLEM. 

 As some interest seems to have been manifested in this 

 " catch for the unwary," perhaps I may be permitted to hint 

 to " A. P. T." that a neater way of putting the statement, and 

 one, sounding, too, more astonishing, is to omit altogether 

 the qualifying parenthesis "unless the circles are many 

 thousand miles in diameter," — and to say (instead of the 

 subsequent sentence) : " The difference will never be greater 

 than the circumference of a circle 18 feet in diameter." In 

 fact, owing to the rotundity of the earth, the greater the 

 circles, the less will be the difference between them. Their 

 greatest possible circumference would be attained it they 

 were made to encircle the earth exactly at the Equator, and 

 then their difference would entirely vanish, and they would 

 be equal. M. A. I. 



AURORA BOREALIS. 

 I never saw it recorded that any one had heard this 

 phenomenon, neither have I, although I have seen the entire 

 sky illuminated with the streaks of light, shooting from the 

 northern horizon, with little apparent diminution, to the 

 southern ; but a retired ship captain here informs me that he 

 and others with him often heard a crackling noise accompany 

 it, or a sound resembling sheets of tin being rattled together, 

 particularly near the banks of Newfoundland. 

 North Shields. T, Todd. 



Lamp. — A mineral-spirit lamp has been patented by 

 Mr. W. H. Beck on behalf of Mr. O. Proust. The burner 

 is constructed by means of two combined tubes sliding 

 one in the other to effect the raising and lowering of the 

 wick. A tube perforated throughout its length contains 

 and conducts the wick to the lamp, and thus puts it by 

 means of openings in contact with sponges saturated 

 with the mineral spirit, and leaves it constantly free to 

 be operated on by the regulating apparatus of the 

 burner. 



Electric Clock. — An electric clock has been patented 

 by Mr. J. G. Lorrain. The invention consists in the 

 combination of an electromotor capable of being 

 actuated by continuous currents, and rotating at each 

 transmission of the electric current, and a detent serving 

 to arrest the movement of the electromotor when it has 

 travelled through its required distance, and to allow 

 it to make its next movement in the same direction as 

 before, when the next transmission of electric current 

 takes place. 



Batteries. — An electrical battery has been patented 

 by Mr. C. P. Elieson. The invention consists in the 

 combination of two hollow electrodes of any form, 

 adapted to be placed one within the other. In the case 

 of secondary batteries each electrode is composed of a 

 series of plates of metal superposed, but separated from 

 each other by interposed pieces of suitable porous 

 materia], all the plates being secured in position by rods 

 or suitable means. In the case of a primary battery the 

 electrodes are built up in a similar manner, except that 

 the porous material is not required, the plates being kept 

 separate by distance pieces. 



Advertising. — An apparatus for exhibiting advertise- 

 ments has been patented by Mr. F. Schoyer. The 

 apparatus is contained in a box glazed in front, through 

 which the advertisements are seen. The advertise- 

 ments are made into a continuous sheet and passed 

 round rollers, so that it is held distended where it appears 

 opposite the glass front, but where it is out of sight it is 

 allowed to accumulate in folds. On the periphery of 

 the upper rollers are fixed pegs, which engage in eyelets 

 made at regular distances apart in the advertisement- 

 sheet, so that when the rollers are revolved by means 

 of a handle or other motive power, automatic or not, the 

 advertisements appear in view successively as the sheet 

 is drawn forward. 



Filter. — A pocket filter has been patented by Messrs. 

 S. W. Silver and W. S. Bennett. This filter is so con- 

 structed that when not in use it can be folded up and 

 carried in the pocket. It consists of a box with a per- 

 forated base, the inner surface of the base being covered 

 by a piece of flannel on which is placed a block of char- 

 coal which has another piece of flannel placed on top of it. 

 This latter piece has a hole in its centre for the block 

 nozzle to project through to enable the suction tube to be 

 attached. A screw cover rests upon the top flannel below 



