GEOPHYSICAL LABORATORY. 133 



(14) An improved form of thermo-regulator. John B. Ferguson. J. Am. Chem. Soc, 



40, 929 (1918). 



This regulator differs from the usual type in that the coarse and fine ad- 

 justments are made by means of a plunger and plunger-tube which regulate 

 the height of the mercury in respect to a fixed platinum wire. 



(15) The work of the Geophysical Laboratory. Robert B. Sosman. Am. J. Sci., 46, 



255-258 (1918). 



A brief statement of the plan and an outline of the results of the Labora- 

 tory's work on mineral systems, prepared for the chapter on mineralogy in 

 the anniversary number of the American Journal of Science. 



(16) The place of manganese in the periodic system. F. Russell v. Bichowsky. J. Am. 



Chem. Soc, 40, 1040-1046 (1918). 



The older arguments placing manganese in the seventh group of the periodic 

 system (i. e., giving manganese a normal valence of 7) now appear open to 

 question. On the other hand, there are 12 different lines of argument based 

 on purely chemical relationships which indicate its position in the eighth 

 group. This conclusion is also in accord with the more decisive reasoning 

 based on atom color presented in a previous paper. (See "The color of 

 inorganic compounds," reviewed under No. 6.) 



An improved form of the periodic table, showing the relations of the 

 eighth and rare-earth groups to the rest of the periodic system, is presented. 



(17) Temperature uniformity in an electric fm'nace. John B. Ferguson. Phys. Rev., 12, 



81-94 (1918). 



The problem of temperature uniformity in an electric furnace is intimately 

 connected with almost all investigations carried on at high temperatures. 

 For this reason it has generally been considered as a part of a larger problem 

 and has been solved to the extent demanded by the requirements of the work 

 at hand. In this paper the writer presents a more general discussion of the 

 subject, together with many results obtained by him in his various investi- 

 gations bearing directly thereon. 



The production of temperature uniformity in an electrically heated air- 

 column may best be done by means of three independent heaters and end- 

 plugs. The entire region to be heated should be surrounded by a layer of 

 conducting material sufficient to smooth out any local heatings and the whole 

 furnace so insulated that the effect of non-uniformity in the temperature of 

 the furnace surroundings is rendered negligible. The use of alternate layers 

 of good and poor conductors will reduce the total amount of insulation neces- 

 sary, but if constancy of temperature as well as uniformity is desired, the 

 insulation must be of such thickness as to eliminate the effect of temperature 

 fluctuations in the furnace surroundings during the period the furnace is in 

 use. This type of furnace has the advantage that it may be converted into a 

 simpler type if less uniformity is adequate by merely changing the mode of 

 connecting the heaters. 



A furnace embodying these principles is described in detail. This furnace 

 yielded a temperature uniformity of ±0.5° C. at temperatures ranging from 

 620° to 1190°, and at 1000° and 1190° C. a temperature constancy of ±0.25° 

 for periods of time exceeding an hour. With greater care in adjustment a 

 uniformity of ±0.2° C. should be possible, and without doubt the furnace 

 could be run at much higher temperatures without great loss in efficiency. 

 The furnace is economical of current and will reproduce practically the same 

 conditions on different days with the same amount of current, provided the 

 temperatures are below that at which magnesia powder begins to pack. 



