566 



POPULAR SCIENCE MONTHLY. 



temperature upon health, and its range 

 is of more importance tlian its mean. 

 The European under a tropical climate 

 suffers from anaemia, diseases of the di- 

 gestive system, especially of the liver, 

 from malaria, dysentery, typhoid fever, 

 and yellow fever. It is not at all easy 

 to say, however, how much of the excess 

 of mortality of Europeans in tropical 

 and subtropical countries is simply at- 

 tributable to climatic heat per se, and is 

 consequently inevitable and not the ef- 

 fect of malaria, or how much of it is the 

 direct consequence of habits of life and 

 of the neglect of sanitary laws and of 

 personal hygiene. As Arnould rightly 

 said, the habitudes alimentaires of the 

 Anglo-Saxon constitute one of the stum- 

 bling-blocks to health, but by far the 

 most important is malaria, compared 

 with which the rest are relatively insig- 

 nificant. Mr. Chamberlain was right 

 when he said the other day that ' the 

 man who sliall successfully grapple with 

 tliis foe to humanity and shall find a 

 cure for malarial fever and shall make 

 the tropics livable for the white man, 

 will do more for the world and more for 

 the British Empire than the man who 

 adds a new province to the wide domin- 

 ions of the Queen.' " 



" Picture Telegraphy." — The fol- 

 lowing account of the new so-called pic- 

 ture telegraphy is from the New York 

 Electrical World and Engineer: "The 

 apparatus consists of a receiver and 

 tran.smitter, similar in appearance and 

 in mechanism. The picture to be trans- 

 mitted is drawn on a heavy piece of 

 metal foil, the lines of the drawing being 

 made with an insulating ink. The foil 

 is then secured on the circumference of 

 a horizontal cylinder on the transmitter, 

 the cylinder being of about the size of 

 a typewriter rubber roller. There is a 

 similar cylinder on the receiver, on 

 whose surface is clamped the paper upon 

 which the drawing is to be reproduced; 

 over this is superposed carbon paper, 

 which is covered in turn by a sheet of 

 thin paper. A stylus actuated by an 

 eUictro-magnct is adjusted close to the 

 surface of the latter, and each time a 

 current is passed through the electro- 

 magnet the stylus is forcibly pressed 

 against the moving surface of the cylin- 

 der, and a corresjionding mark is made 

 on the two sheets in contact with the 



carbon paper; the outer sheet serves 

 merely to offer a smooth surface to the 

 stylus and to enable the operator to see 

 that the picture is being properly repro- 

 duced. The transmitting cylinder passes 

 under a similar stjdus, which latter 

 closes the circuit between the receiving 

 and transmitting ends when it rests upon 

 the foil, and opens the circuit when it 

 passes over the lines drawn with insu- 

 lating ink, in the latter case actuating 

 the stylus magnet at the receiving end, 

 which leaves a mark on the paper of the 

 receiving cylinder in the form of a line 

 corresponding to the width of the insu- 

 lation over which the transmitting sty- 

 lus is passing. The stylus at each end of 

 the line is simultaneously advanced at 

 the end of each revolution of the cylin- 

 ders by a screw of small pitch. From the 

 description it will be seen that if the sur- 

 face of the foil on the transmitting cyl- 

 inder were entirely insulated the receiv- 

 ing stylus would merely draw a number 

 of parallel lines on the paper correspond- 

 ing to the turns of the screw, and sepa- 

 rated a distance corresponding to the 

 pitch of the screw and the angle through 

 which it is turned at each operation. 

 Four different rates of advance may be 

 given to the stylus, corresponding to as 

 many different angles of advance that 

 may, by appropriate mechanism, be 

 given to the screw. The two cylinders 

 have synchronous motion, so that all the 

 marks or lines on the receiving cylinder 

 correspond to widths of insulating ink 

 traced over on the transmitting cylinder. 

 Synchronism is obtained as follows: Con- 

 nected with both receiver and trans- 

 mitter is an electric motor which, at the 

 end of every revolution of the cylinder, 

 raises a weight, which acts on a clock 

 train when failing and thus gives motion 

 to the cylinder. At the end of each revo- 

 lution of the transmitting cylinder a 

 contact is made whieii locks for an in- 

 stant the receiving cylinder when it ar- 

 rives in a position corresponding to a 

 similar position of the transmitting cyl- 

 inder. Thus it will be seen that each 

 cylinder begins its revolution from iden- 

 tical ])ositions and at the same instant, 

 and as the clockwork of both receiver 

 and transmitter are dtiplicates, approxi- 

 mate synchronism is maintained during 

 a revolution. Owing to the Tise of car- 

 bon paper, the linos made by the receiver 

 are of considerable width, with the con- 



