694 



SUMMABY OK ( UKKENT RESEARCHES RELATING TO 



place the cylinder on the observer's left, so that he can with his left 

 hand regulate the outflow of gas. The whole chamber is clamped to the 

 Microscope. With a continuous stream of gas a temperature of —30 0. 

 is quickly and easily attained. The author has not found any injurious 

 results happen to his lenses. 



Fig. 79. 



Leiss' Universal Spectral Apparatus.* — This apparatus has been 

 constructed by the firm of Fuess, and many of its novelties have 

 been suggested by J. Koenigsberger. The instrument is intended to 

 be available for observations upon emission spectra, absorption spectra, 

 Zeeman effects, wave motions, and measurements of layer thicknesses. 

 Fig. 80 gives a general view of the apparatus, and fig. 81, which is a 

 horizontal section through the collimator and the telescope, represents 

 the optical arrangements. The bearer A of the observation-telescope is 

 rotatory about a conical vertical axis carried on a strong tripod fitted 

 with levelling screws. The bellows also, as far as possible, take part 

 in this rotatory movement. The lever screws a clamp A, while the 

 micrometer-screw a^ operates the fine-adjustment. Connected with this 

 is a drum graduated into 150 equal parts, each part corresponding to an 

 angular distance of 10". A large loup L facilitates the reading of the 

 drum divisions, an electric glow-lamp e for 2 or 4 volts serving as an 

 illuminator. The load of the bearer A is counterpoised by the weight g. 

 In the above-mentioned conical axis a conical plug is inserted, rotatory 

 by means of the milled head K for adjusting the prism-table, which is 

 clamped on to the plug by the screwy. The screw k 1 clamps the axis of 



/.(it. f. tnst rumen tenk., xxx. (1910) pp. 353-7 (2Jfigs.). 



