SCIENCE- G OSSIP. 



CONDUCTED BY JAMES QUICK. 



Electric Tramways ix Paris. — Visitors to 

 Paris at the present time are finding the electrical 

 tramways and railway a great boon. There are 

 five stations on the latter system, which fringes the 

 Exhibition. For 25 centimes a good view of the 

 exterior of the buildings and the environs of the 

 extensive area covered by the Exhibition can be 

 obtained with ease and comfort. The means of 

 getting about the city by the tramways is very 

 complete. The only forethought necessary is to be 

 provided with a ticket before attempting to enter a 

 car, as without it the chance of securing a seat is 

 practically impossible. 



The Structure of Metals. — Some very im- 

 portant work has recently been done by Professor 

 J. A. Ewing and Mr. W. Rosenhain upon the micro- 

 scopical examination of the surfaces of metals, 

 subjected to various physical changes. Professor 

 Ewing gave a very lucid account of some of 

 these researches at the Royal Institution on 

 May 18th. Every metal or alloy under various 

 physical conditions reveals, when examined under 

 a powerful microscope, a definite granular or 

 even crystalline structure, which cannot be 

 permanently effaced. Even in a substance such 

 as lead, which might from first thoughts be 

 assumed to have no definite structure at all, 

 geometrical form and uniform design are found. 

 Professor Ewing explains the plasticity of metals 

 by the slipping of the granular crystals more or 

 less readily over each other. A further interesting 

 point is the "growth" of these structures. If a 

 metal, say lead, is greatly compressed, the surface 

 reveals a somewhat irregular granular structure, 

 the size of the granules being small. After certain 

 periods, depending upon heat and other conditions, 

 these small granules graduallv coalesce and in- 

 crease considerably in size. They are then found 

 to have again assumed the original structure of the 

 untreated lead. 



A New X-Ray Localiser. — A new method of 

 localisation in X-ray work has recently been 

 devised by Professor F. R. Barrell. In all methods 

 of localisation of foreign bodies it is essential that 

 two distinct radiographs should be taken. This is 

 done by changing the position of the X-ray tube, 

 the distance through which it has been moved 

 being ascertained. The points upon the photo- 

 graphic plate where it is met by lines drawn per- 

 pendicular to it from the focus of the tube are 

 located, in hitherto existing methods, by the use of 

 a plumb-line, necessitating, among other things, 

 levelling the plate. In Professor Barren's method 

 no plumb-line, no threads, and no levelling are 

 required. Two metal cylinders are used that have 

 their ends carefully turned perpendicular to their 

 axes. The size of these cylinders is about 4 inches 

 lone and 1 inch diameter. They are placed up- 

 right on the plate during the exposure. The 

 shadows thrown by the cylinders are utilised to 



locate the position of the focus of the tube. After 

 the first excitation the tube is shifted about 

 8 inches, the cylinders are also shifted towards the 

 opposite end of the plate, and then the second ex- 

 posure is made, giving rise to the second set of 

 shadows from the foreign body and the cylinders. 

 Lines are now ruled along the edges of the 

 shadows of the cylinders, when these were in the 

 first positions, and produced till they meet. The 

 point of crossing gives the point on the plate 

 which was perpendicularly beneath the focus of 

 the tube during the first exposure. The same 

 process is gone through with the second set of 

 shadows to find the perpendicular point below the 

 focus in the second position. All the necessary 

 data are thus obtained to accurately locate the 

 position in space of the foreign body. The beauty 

 of this method is that it is so very simple. The 

 necessary apparatus costs practically nothing, for 

 two metal bars of square section will serve equally as 

 well as the cylinders, provided they have well-defined 

 edges and flat ends, so that they will stand upright. 



Kites axd Ballooxs ix Meteorology. — Some 

 useful work is now being carried on in the study 

 of the upper atmosphere by means of kites and 

 balloons. In September last, observations were 

 made at an altitude of 4,300 metres, the highest 

 hitherto attained by any form of kite. It is now 

 also possible to send up small balloons during 

 strong gales, even in a wind with a velocity of 

 14 metres per second. These captive balloons have 

 attained much greater altitudes than the kites, 

 but a difficulty is encountered by the heating- 

 action of the sun. By working at night, by moon- 

 light, over 120 balloons have been launched, by 

 means of which the curves of temperature and 

 pressure have been automatically registered at a 

 height of 13,000 metres on twenty-four occasions, 

 at 14.000 metres eight times, and at 15,000 metres 

 three times. 



Lichtexberg Figures. — Every student of 

 electricity knows the beautiful figures that may be 

 produced upon a plate of resin or vulcanite by 

 tracing a design upon it first with the charged 

 knob of a Leyden jar, and secondly with the outer 

 coating, and then dusting a mixture of red lead 

 and sulphur upon it. The sulphur will attach itself 

 to the positive lines, and the red lead to the negative 

 lines. Instead of using the above mixture, one can 

 be made up with 1 part by volume of carmine, 

 3 of lycopodium, and 5 of flowers of sulphur. The 

 carmine and sulphur are first thoroughly mixed. 

 and the lycopodium is added last. The figures are 

 reversed in colour with respect to the ordinary 

 Lichtenberg figures, as the polarity of the sulphur 

 is reversed in the combination. The figures are of 

 striking beauty ; the circles have centres, and outer 

 rings of the opposite colour. 



Paris Coxgress. — The Paris International Con- 

 gress of Electricity will be opened on Saturday, 

 August 18th, at 10 a.m., in the Palais des Congres. 

 Paris, and will remain open up to the 25th. It 

 will consist of the following five sections, under 

 separate presidents : I. Scientific Methods and 

 Measuring Apparatus ; II. Generation, Trans- 

 formation. Transmission and Distribution of 

 Electric Energy ; Electric Lighting and Traction ; 

 III. Electro-chemistry ; IV. Telegraphy, Telephony, 

 k.c. ; V. Electro-physiology. During the Congress 

 visits will be made to the various installations in 

 Paris, in which only members will be allowed to 

 take part. 



