Chemistry and Phys%cs. 483 



with suitable wax. The cover is pierced by four holes through 

 which two electrodes and two tubes pass. The negative wire is 

 sealed in a glass tube which allows only the lower end of the 

 wire to project a few millimeters. This electrode is placed close 

 to the inner wall of the tumbler and it runs down almost to the 

 bottom of the vessel so as to have the exposed end of the wire 

 immersed in the solution containing the metal, the spectrum of 

 which is desired. The positive electrode has the same form and 

 it coincides with the axis of the tumbler. The tip of the positive 

 wire is adjusted so as to leave a spark-gap of a few millimeters 

 length above the free surface of the liquid. To secure adequate 

 insulation the capillary tube containing the positive wire is sur- 

 rounded by a glass tube of much larger diameter which projects 

 several centimeters both above and below the wooden lid. The 

 wires are composed of iron or aluminium. The inlet tube for 

 air under pressure runs down near the negative terminal to 

 within a centimeter or two of the liquid surface. The outlet 

 tube is flared at the receiving end which is just below the wooden 

 lid and diametrically opposite to the inlet tube. 



The collector is simply an inverted glass funnel closed by a 

 wooden disk. Since six sprayers can be used with the same 

 burner, there are six holes in the disk through each of which the 

 outlet tube from a sprayer passes. The upper part of the funnel 

 is joined by a short section of rubber tubing to a glass four- 

 branch tube. The axial extension of the funnel tube passes 

 through a stopper at the lower end of the coaxial mixing cham- 

 ber. The two branches of the glass cross, that are at right 

 angles to this axis, admit oxygen on one side and coal gas on 

 the other. 



The mixing chamber is made of a brass tube 2.2 cm in diameter 

 and 15.2 cm high. The top of this tube which constitutes the 

 burner consists of a brass disk 6 mm thick through which one 

 or more holes are drilled. Each hole should have a diameter 

 not exceeding 2 mm. One hole is generally sufficient, but four 

 holes pierced close together at the vertices of a square produce 

 a more brilliant resultant flame. 



All the inlet tubes of the sprayers branch from one air-supply 

 tube. Since all connections are made with sections of rubber 

 tubing the sprayers can be started, regulated, or stopped by 

 pinch-cocks. The positive electrodes are all permanently con- 

 nected to one coating of a pint-size Ley den- jar. The negative 

 terminals can be successively connected to the other coating of 

 the condenser. An induction-coil giving a 15 cm spark is suf- 

 ficient for working the sprayers. The flames should be from 

 30 to 45 cm high and not more than 1.3 cm in diameter. The 

 cone should not exceed 2.5 cm in length. 



"The flames obtained in this manner are exceedingly well 

 suited for showing, in a large lecture theatre, the spectra of the 

 more volatile elements, such as Ca, Sr, K, Cu, &c., to an audience 



