On a new Form of Constant- Temperature Bath. 339 



were on occasions deceived by the presence of a concealed 

 aurora, and thus the zodiacal light and the aurora spectra 

 were at first confounded. Seeing, also, how up to the present 

 time we have quite failed to produce in our laboratories 

 any form of electric discharge which by its spectrum can 

 fairly be pronounced as of an auroral character, it would seem 

 desirable to wait the result of later and fuller particulars from 

 the learned Professor before passing a definite judgment on 

 the matter. We do not at present hear of any compari- 

 sons of the "artificial" aurora-spectrum with other spectra 

 which will explain its true and so long hidden character; 

 though doubtless, if we can succeed in establishing an aurora 

 " en permanence," good results may reasonably be expected 

 to follow, one principal cause of failure in explanation of the 

 Aurora mystery being the infrequency of the opportunities 

 afforded of examining its spectrum and comparing it directly 

 with others. 



Guildown, April 6, 1883. 



XL VIII. A neiv Form of Constant- Temperature Bath. By 

 W. W. J. Nicol, M.A., B.Sc., F.R.S.E., Lecturer on 

 Chemistry, Mason College, Birmingham *. 



THE want of a simple and, at the same time, reliable con- 

 stant-temperature bath has been felt by all who have 

 made specific-gravity determinations. The following ap- 

 paratus, which has been found thoroughly efficient, was 

 devised by me during the course of my experiments on the 

 specific gravity of salt-solutions, the results of which have 

 been recently published f. 



The apparatus consists of three parts — the bath, the heating 

 arrangement, and the thermostat. The bath is of copper, 

 measuring 200 millim. in length, 200 millim. in depth, and 

 90 millim. in width — a size I found most convenient for use 

 with the Sprengel tubes described in the ' Chemical News ' 

 (February 1883). Near one end is soldered a wide brass 

 tube (0, fig. 1) with a slot down one side: this is intended to 

 receive the thermostat and thermometer. The water in the 

 bath is agitated by means of a current of air supplied by a 

 Fletcher's blower. The air escapes from a perforated tube 

 lying on the bottom of the bath. 



* Communicated by the Author. 



t Proceedings Roy. Soc. Edin. 1881-82 ; Ber. deut. Chem. Ges. 1882, 

 p. 1931; Phil. Mag. 1883, February; Chem. Soc. Joum. 1883, March. 



