102 Prof. R. Shida on a new Instrument for recording the 



successively come into contact with the column of water be- 

 tween the capillary plates. Every time any one of the platinum 

 teeth comes in contact with the water, it closes an electric 

 circuit (to be described) corresponding to it, so that these 

 platinum teeth may be called " circuit-closers/' 



(L) is a cylinder of wood lacquered all over. It is covered 

 with platinum sheet, and on this sheet is rolled a ribbon of 

 white paper nearly as wide as the length of the cylinder. A 

 portion of this cylinder is in the rectangular box (B), which 

 contains a chemical solution, consisting of ferrocyanide of 

 potassium, nitrate of ammonium, and water mixed in a 

 certain proportion. Further, the cylinder (L) is made to 

 revolve with uniform velocity by means of a clockwork 

 arrangement placed inside the box (H). Thus the paper on 

 the cylinder, as it rotates, comes out moistened with the 

 chemical solution. Resting on the cylinder (L), and fitting 

 tightly in a rod of ebonite (r), there are a number of platinum 

 needles n, n, n, &c. ; these needles may be called "mark- 

 ing-needles/' for, if an electric current passes between any of 

 these platinum needles and the revolving paper, a bluish mark 

 is made on the paper directly underneath that needle. 



These marking-needles are electrically connected, each to 

 each, with the circuit-closers in order, there being as many 

 needles as there are circuit-closers ; that is to say, the first 

 needle (on the right or left) is in connection with the first 

 circuit-closer (on the right or left), the second needle with 

 the second circuit-closer, the third with the third, and so on. 

 The small terminal screws, a, a, a, &c, on the ebonite 

 plate (E), which is fixed to the framework of the apparatus, 

 and also the screws, b, b, b, &c, are provided for facilita- 

 ting these connections. The exceedingly fine wires (insulated) 

 connect the screws a, a, a, &c, with the circuit-closers, 

 and they all hang down from the screws in the form of spiral 

 springs, meeting together in the common axis of the disk (D), 

 and the coil (C), and thence go to the circuit-closers ; so that 

 it is to be understood that the resistance these wires offer to 

 the motion of the disk and coil is so small as to be negligible. 



Now, the platinum sheet on the cylinder (L) is in connec- 

 tion with one pole (Z) of the battery (CZ), by means of a pla- 

 tinum spring (s) resting on it ; while the other pole (C) of 

 the battery is in connection with the capillary plates (see fig. 

 3). Consequently, when there is no current passing through 

 the coil, the positive current flows from the copper pole of 

 the battery through the capillary plates, and the circuit-closer 

 in the centre, and thence through the corresponding marking- 

 needle (the centre one), rotating paper, and platinum sheet, 



