122 



SCIENTIFIC NEWS. 



[Aug. 10, li 



high, the top having the appearance of being broken off ; 

 i to 60, hardly possible to distinguish anything above 

 the oil flame. The colliery firemen to which this latter 

 was shown " asserted positively that they would con- 

 sider an atmosphere in which the small oil flame burned 

 as it did in this mixture to be perfectly free from gas." 



It is evident from these experiments that, in the ordi- 

 nary course mines may be reported to be free from fire- 

 damp in which the air is mixed with 1 part in 60 or any 

 smaller proportion. 



Mr. Galloway found that ordinary coal-dust mixed 

 with air only is not inflammable at ordinary pressure 

 and temperature, but that if air be mixed with fire-damp 

 in proportions of one in 112 and in greater proportions 

 it becomes inflammable at ordinary pressures and tem- 

 peratures. From these results, together with those of his 

 experiments on the lamp-flame, it is evident that mines 

 with an atmosphere containing any proportion of fire- 

 damp between ttj and iti may be reported free from 

 fire-damp, and yet be very dangerous, owing to the com- 

 bined operation of the coal-dust and the small proportion 

 of hydro-carbon gas. This may have been the condition 

 of the Campagnac Colliery above referred to. 



There is a curious fact connected with colliery explo- 

 sions in dry mines, which at first glance appears 

 mysterious, but which is readily explained when the 

 potency of coal-dust in producing them is understood. 

 It is that they occur most frequently in the winter 

 months when the air is coolest. 



This is due to the fact that in coal-mines generally the 

 temperature below is subject to very little variation. It 

 is regulated by the rock temperature, not by that of the 

 atmosphere above ground. I knew an old collier in 

 Flintshire who had saved enough to buy a small 

 freehold and retire, but who worked below in the 

 winter for comfort's sake, or, as he said, for the benefit 

 of his health, just as more luxurious patients winter 

 at Mentone or San Remo. To explain this let us suppose 

 the case of a deep pit at 70 degs. Fah. With the sum- 

 mer air above ground at 70 degs. and saturated with 

 aqueous vapour, it will remain thus saturated below ; 

 but in winter the air, say at 40 degs. and also saturated, 

 will when raised to 70 degs. below acquire a propor- 

 tionately increased capacity for water, and will be very 

 dry and thirsty, taking water from everything it touches 

 that is at all damp. It will thus render the loose dust 

 excessively dry, and thereby increase its inflammability. 



It will be further understood from the above-stated 

 facts that thorough ventilation, which is the best safe- 

 guard against the accumulation of fire-damp, may 

 contribute to the explosiveness of coal-dust. 



It is evident, therefore, that in working the deeper 

 collieries of the future our mining engineers will have 

 to study these modified conditions of danger, and make 

 arrangements accordingly. The watering of mines will 

 become as necessary then as the pumping is now ; such 

 watering will be demanded not only for laying the dust, 

 but also for lowering the temperature of the workings. 



Volcanic Eruption in the Lipari Islands. — On 

 August 3rd an eruption occurred in these islands, on 

 which the well-known volcano of Stromboli is situated. 

 Immense damage is stated to have been caused by the 

 eruption, but no details have reached here owing to the 

 destruction of the telegraph communicating with the 

 islands. 



REPRODUCTION OF ARTICULATE 

 SPEECH AND OTHER SOUNDS. 



'THE transmission of articulate speech, wonderful and 

 useful as it is, is fully equalled in point of novelty 

 by the instrument for recording, preserving, and produc- 

 ing speech. Without doubt these " speech reproducers " 

 are destined sooner or later to take a large place in business 

 and social transactions. No one who has given the 

 matter a moment's thought will fail to see the utility of 

 a practical machine of this sort. Leon Scott long ago 

 devised a simple and curious instrument known as the 

 phonautograph, in which the vibrations of a diaphragm 

 were recorded by a stylus upon a smoked cylinder, but 

 it is now known that its record was not autographic, 

 although it conveyed a fair idea of the number and variety 

 of air waves necessary to the production of words and 

 sounds. Faber's talking machine is curious and in- 

 teresting on account of being a mechanical imitation of 

 the vocal organs. It is capable of producing articulate 

 speech by the manipulation of a bellows and key. The 

 first machine to really echo one's own words was the 

 Edison phonograph, which, as originally presented, 

 was not sufficiently effective in its operation to be of any 

 great commercial value, although it contained the germ 

 of the modern talking machine. The graphophone, 

 which is shown in the annexed engravings, is, as its name 

 indicates, a recorder and reproducer of sounds. It is the 

 invention of Mr. Charles Sumner Tainter, and is the 

 result of several years' experimentation and the subject 

 of many patents, several of which were issued in May, 

 1886. In its construction efficiency has, of course, been 

 the first consideration, after which the matters of simplicity, 

 facility of management, and the practical handling of the 

 records or messages have been disposed of. The 

 machine is an exceedingly simple thing. Fig. 1 

 shows it as arranged for receiving or recording the 

 message. The frame of the machine consists of end 

 pieces connected by longitudinal rods, In the top of 

 the frame is a fine screw parti}" enclosed by a tube ; the 

 screw is driven through a train of spur wheels attached 

 to the main shaft, which is also provided with a conical 

 chuck. At the opposite end of the frame is a spindle 

 acted on by a spring, which also carries a conical chuck 

 of the same form and size as that on the main shaft. 

 The cylinder upon which the speech is to be received 

 is placed between these chucks in much the same 

 manner as the bobbin is placed in the bobbin winder of 

 the sewing machine, the cylinder being revolved by the 

 frictional contact with the chuck on the main shaft. At 

 the right hand of the instrument is arranged a small rock 

 shaft provided with a cross arm and two keys by which 

 the driving wheel is thrown in and out of connection 

 with the gearing of the machine. On the tube which 

 encloses the feed screw is placed a saddle provided with 

 a follower which enters the slot of the tube, and engages 

 the feed screw. The saddle carries a diaphragm cell, in 

 which is arranged a diaphragm provided with a cutting 

 stylus which engraves the record on the surface of the 

 cylinder. To the diaphragm cell is attached a bar or 

 bridge piece of metal, which extends across the face of 

 the diaphragm, but not in contact with it. This device 

 rests upon the record cylinder a little in advance of the 

 cutting stylus, and supports the weight of the diaphragm 

 cell and its attachments. The depth to which the stylus 

 penetrates the surface of the C3'Iinder is regulated and 

 maintained by this arrangement, and as the bridge-piece 

 bears upon the cylinder near the point of the cutting, 



