THE KAP-TENT WAGON. 669 



served, except, perhaps, in the form of a reduced model. The 

 length ot the wa^on was about 15 feet ; the heiglit of the tilt from 

 the fioor 5 feet 5 inches. Ihe upper rails of the sides, leer- 

 boumen, were curved upwards from about the second third, this 

 being compensated by the kap leer, so that the height of the' roof 

 was the same throughout. The sides stood upon the schammels, 

 and were supported outwardly by the rongen, or struts, which 

 were tightly morticed into the projecting ends of these; inward 

 pressure was resisted by a board through which the posterior 

 projections of the leerboomen were passed. The boogen, or tent 

 bows, arched between standcrs, or standards, which were fastened 

 on the outer sides of the leer-boomen ; two bows to each standard, 

 holding between them the laths which supported the canvas 

 covering or zeil. This was double, the onder ::eil being painted 

 to render it water-proof, the boven sell, or upper covering, being 

 of white canvas and furnished with voor and achter klaps, fore 

 and hind flaps, to be let down when it rained, or at night. The 

 principal furniture consisted of the kartel, or bunk, suspended 

 between the two sides, and the voor-kist, or fore-chest, which 

 served the double purpose of providing the driver with a seat 

 and preserving the more precious of the family goods. 



The Geophone.— The Journal of the Franklin Institute'^ 

 contains a communication from the United States Bureau of 

 Mines descriptive of the geophone, a listening instrument in- 

 vented by the French during the war to detect sapping and 

 mxining operations, and for the location of enemy artillery. It is 

 now being used by the United States Bureau of Mines as a 

 possible aid in locating miners who have been entombed after a 

 disaster. The instrument is essentially a small seismograph. It 

 consists of an iron ring about 3/^ in. in diameter, within which 

 is suspended a lead disc fastened by a single bolt concentrically 

 to two mica discs, one of which covers the top and the other the 

 bottom of the ring. Two brass cai>pieces cover the discs, the 

 top one having an opening in its centre, to which is attached a 

 rubber tube leading to a stethoscopic ear-piece. These cap-pieces 

 are fastened with bolts to the iron ring, and serve to hold the 

 mica discs in place. Essentially the apparatus is merely a lead 

 weight suspended between two mica discs cutting across a small 

 air-tight box. If the instrument is placed on the ground, and 

 anyone is jxDunding or digging in the vicinity, earth waves 

 shake the geophone case, the lead weight, however, remaining 

 comparatively motionless. A relative motion is thus produced 

 between the instrument case and the lead weight, and as a result, 

 a compression and rarefaction of the air in the instrument takes 

 place. Through the rubber tube this compression and rarefac- 

 tion is carried to the ear-piece.' Direction of the source of dis- 

 turbance may be quite accurately ascertained by using two 

 instruments, as the sound is apparentl}^ louder from the instru- 

 ment nearer that source. 



187 [5], 580 (1919). 



