APPENDIX. 449 



telephone spoken to), and that the diaphragm is valuable for the 

 purposes of strengthening the sound ( 444, b) and transmitting it to 

 the ear of the listener. The scientific paper, Nature, says that care- 

 ful investigation leads to the conclusion that, at the sending station, 

 the evidence of molecular action, though suggestive, is by no means 

 conclusive, whereas, at the receiving station, the existence of molec- 

 ular as well as mechanical action amounts to demonstration and is 

 shown to be considerable in amount. 



APPENDIX N. 



The Phonograph. (See 447.) The appearance of this in- 

 strument is shown in the accompanying cut, in which F represents 



FIG. 447- 



the mouthpiece ; C, the cylinder covered with tin-foil ; E, the axis 

 with a thread working in A, one of the two supports. The mouth- 

 piece, with its diaphragm and style, may be moved toward the 

 cylinder or from it, by means of the supporting lever, HG, which 

 turns in a horizontal plane about the pin /. 



APPENDIX 0. 



Differential Thermometer. (See 482.) Prepare two 

 boards, each 5x7 inches and an inch thick. Place them upon end 

 parallel to each other, 7 inches apart. Connect the boards by 

 nailing to their tops two thin strips, each an inch wide and 9 inches 

 long. The strips will be 3 inches apart. This is our stand. For 

 the two bulbs use two tin oyster cans with flat sides. To the centre 

 of one end of each solder a tin tube, 1| inches long and f of an 



