Dec, 1904.] 



KN(MVI KHGE & SCIENTIFIC NEWS. 



297 



powerful beam of light, and here is certainly an interest- 

 ing exhibit, although the system has been before the 

 scientific world for some years. From a practical point 

 of view, the invention may seem disappointing, for at the 

 transmitting end a man shut in a sound-tight cupboard 

 blows a loud bugle, the sound of which is conveyed by 

 the searchhght to a distance of only 150 feet, when it is 

 received on a silenium cell, and is very faintly audible in 

 a telephone receiver. The other wireless telephone is on 

 the Miller- ReeceHutchison system, in which the trans- 

 mitter is connected with a large coil of wire underground, 

 and the receiving telephone with a coil held in llie hand. 



Elsewhere exhibits are given of the properties of liquid 

 air and of thermit, extremes of cold and heat which may 

 not be familiar to many visitors. 



Of course, several methods of obtaining photographs 

 in natural colours are to be found among the profusion of 

 exhibits. Mr. Cowper Coles shows specimens of electric- 

 ally deposited metals and the differences of surface 

 obtained by rotating the cores at various high speeds 

 while the coat is forming. 



LEFT EYE 



RICH! Ere 



Dia^am to show how one eye sees one series of stripes while 

 the other sees only the other series. 



The Delaney system of rapid automatic telegraphy is 

 one of the interesting novelties shown. This is a perfo- 

 rated tape machine designed to overcome the tendency 

 existing in other machines of this sort to blur the dots 

 and dashes when sent over a long line. In the perforat- 

 ing apparatus the depression of the key causes a magnet 

 to operate a punch near the upper edge of the tape, while 

 the release of the key brings into operation a punch near 

 the lower edge, so that as the tape is travelling forward 

 the dots and dashes are distinguished by the angular dis- 

 tance of the holes. In the transmitting machine the 

 upper holes give connection to a positive current, while 

 the lower ones give a negative current ; so that impulses 

 are sent through the line which are not blurred by the 

 static capacity of the cable. It is said that in laboratory 

 experiments messages have been sent at the rate of Sooo 

 words per minute, and even over lines 1000 miles long a 

 speed of 1000 words a minute has been attained. 



A fascinating instrument to watch is the Telautograph, 

 for reproducing at a distance handwriting, sketches, and 

 similar matter — in fact, a " writing telegraph." The 

 transmitting and receiving instruments are so arranged 



that ; n the latter moves synchronously with the 



transiuiiimy pencil. The operation is as follows : — 



-At the transmitter the sending pencil is attached by 

 two light rods to two lever arms which carry contact 

 rollers at their ends. These contact rollers bear against 

 the surface of two current-carrying rheostats, and the 

 writing currents pass from the rheostats to the rollers, 

 and from them to the line wires. 



When the pencil is moved, the position of the rollers 

 upon the rheostats is changed, and currents of varying 

 strength go out upon the line wires. 



At the receiver these currents pass through two 

 light vertically movable coils, which are suspended in 

 uniform magnetic fields, and which move up or down 

 against the pull of retractile springs, according to the 

 strength of the line currents. The motion of the coils is 

 communicated to a set of levers of the same length as 

 those in the transmitter. At the junction of the levers is 

 mounted the receiving pen, which by the motions of the 

 coils is caused to duplicate the motions of the transmit- 

 ting pencil. 



The paper is supplied from rolls beneath the trans- 

 mitter and receiver, and is shifted off the writing platens 

 as it is used. 



Another machine worth looking at is a Hydro-Pneu- 

 matic Kock Drill in operation, driving holes li inches in 

 diameter through a lump of solid granite at a rate of 

 nearly 6 inches a minute. This runs at a speed of about 

 1000 strokes a minute, the length of stroke being about 

 an inch, and the tool being turned i-iith of a revolution 

 each stroke. 



An interesting system of obtaining a stereoscopic effect 

 by means of a lined screen is exhibited, and, as no descrip- 

 tion of the method seems to have been published before, 

 it may be interesting to describe shortly the general 

 principles involved. 1 1 is called the Parallax Stereogram. 

 Two photographs are obtained by twin stereoscopic 

 lenses in the usual way, except that a screen is interposed, 

 formed of fine parallel lines at intervals equal to their 

 thickness (100 to the inch). Each negative will then 

 consist of a series of stripes. The negatives are 

 then exactly superposed so that the stripe left blank on 

 the one coincides with the stripe containing the picture 

 on the other. Th e resulting image, presenting a most 

 sorry effect, may be seen on opposite page. But if 

 this picture be viewed at a certain distance off, with 

 the screen suitably interposed, the right eye will only 

 be able to see one picture, while the left will only be 

 able to see the other. The result is that the subject 

 appears to stand out in high relief. 



Tiiosr; who have a fondness for Nature in her quieter moods 

 and a love for Natural History will find in " Notes of an East 

 Coast Naturalist," by Arthur Patterson (Methuen) a very 

 charming companion and guide. That the author writes with 

 a first-hand knowledge of his subject is evident, both from the 

 originality of his observations as well as from the spirit of 

 enthusiasm which is manifest in every page. His glimpses of 

 the bird-life of the mud-fiats, marshes, and sea-shore in the 

 neighbourhood of Great Yarmouth are really delightful. We 

 fully sympathise with the author's sentiment against shooting. 

 Though atone time an enthusiastic gunner, he assures us that 

 he had derived far more pleasure in studying the bird-life of this 

 district by the aid of field-glasses. The short sketches con- 

 cerning the fish fauna of his neighbourhood are teeming with 

 interest, and contain some shrewd observations well worthy of 

 careful consideration. As much also maybe said for his notes 

 on the Crustacea of the district. Space forbids a larger notice 

 of this book, l>ut we most heartily recommend it. The coloured 

 illustrations are in many cases extremely good. Hut for the 

 artist's name on the plates,we should have attributed many 

 of the figures of the birds to G. E. Lodge and A. Thorburn. 



