GEOPHYSICAL RESEARCH — DAY. 225 



(4) A large gas-tight bomb for use as a Moissan arc furnace or with carbon 



resistances, in which a gas pressure of 500 pounds can be maintained 

 with temperatures as high as 2500 C. 



(5) An iridium resistance furnace of the Nernst type, intended for heating small 



quantities of mineral to 2100 without the pressure of disturbing carbon 

 products. 



(6) A screw compressor for hand power, with about 1 cubic foot of working space 



and a maximum working pressure of 85 tons. 



(7) An outfit of platinum ware for the chemical section. 



In addition to the above, a hydraulic press, with a suitable gage 

 for pressure measurement, has been ordered in Germany, to be 

 modeled after the one which has been so successfully used by Profes- 

 sor Tammann in Gottingen, which is expected to reach the highest 

 hydraulic pressures obtainable — upward of 3,000 atmospheres — but 

 it has not yet been delivered. f 



Much of this apparatus has been designed and built in our own 

 shop, after some disappointing experience with outside contracts. 

 The shop equipment, which was described in some detail in my last 

 report, has been put to a severe test by these emergencies and has 

 met the demand upon it most satisfactorily. 



The laboratory equipment as it now stands is more intelligibly 

 classified in this way : 



(1) Gas furnaces for the preparation of specimens. 



(2) Furnaces reaching 1600° C, with facilities for the accurate measurement 



of temperature and for work in oxidizing or reducing atmospheres or 

 vacuum. 



(3) A furnace reaching 2100 C. in oxidizing or reducing atmosphere in which 



temperature can be measured. 



(4) A large furnace containing electrodes for arc or carbon resistance heating 



on a considerable scale and with any pressure up to 500 pounds or a 

 vacuum. 



(5) A pressure plant for supplying gas at 500 pounds. 



(6) A pressure plant (Barus) reaching 2000 atmospheres water pressure in a 



very limited space, equipped with pressure gages. 



(7) A water-pressure plant (Tammann) to reach the highest pressure with 



greater convenience and certainty ; also with gage. (Under construc- 

 tion.) 



(8) Arrangements for heating all the above with electricity except (1). 



(9) Complete equipment for the measurement of temperature and for standard- 



izing same. 

 (10) A good shop equipment, both for new construction and repairs. 



SCIENTIFIC WORK OF THE YEAR. 



The scientific work of the year, while the pressure plant was being 

 installed, has been necessarily confined to the study of mineral com- 

 binations under atmospheric pressure. 



Feldspars. — The investigation of the lime-soda feldspar group which 

 was begun in the Geological Survey has been finished, after nearly 

 three years' work upon it. The investigation has shown that the 

 lime-soda feldspars form a continuous series of mixed crystals capable 



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