ge;ophysical laboratory. ioi 



The total loss of heat of the crucible alone (and this includes also the slight 

 loss from the formation of steam as the crucible strikes the water) was only 4 

 per cent. The crucible was dropped electrically (Marker's method) by melt- 

 ing a supporting wire. This was done automatically by the swinging aside of 

 a shield between furnace and calorimeter. The principal source of error ( i 

 per cent or more) was found in the uncertain temperature distribution within 

 the furnace ; a longer and narrower furnace is expected to diminish this. The 

 accidental errors averaged about 0.3 per cent, that is, duplicate results usually 

 agreed as well as this. 



(3) Die Justierung des Abbe-Pulfrischen Kristallrefraktometers. Fred. Eugene Wright. 



Zeitschr. f. Instr. 28, p. 201, 1908. 



A detailed statement of the adjustments which are necessary to establish 

 the magnitude of the errors occurring in the use of the Abbe-Pulfrich crystal 

 refractometer. In this paper serious exception is taken to the practice very 

 generally indulged in by instrument makers of concealing adjustment screws 

 with the intention of preventing any adjustment of the instrument after it 

 leaves the factory. Where apparatus is intended for rough or rapid work, or 

 for classroom demonstrations, where high accuracy is not sought, such a 

 practice is more or less justifiable and tends to prevent the apparatus from 

 being tampered with by inexperienced students ; but it becomes a serious lim- 

 itation in the use of a measuring instrument for research work if its errors 

 can not be promptly and accurately determined or if it can not be quickly and 

 conveniently readjusted when necessary. 



(4) The role of water in tremolite and certain other minerals. E. T. Allen and J. K. 



Clement. Amer. Jour. Sci. (4), 26, p. loi, 1908. 



A study of five difterent specimens of natural tremolite. two of them of ex- 

 ceptional purity, proves that all contain water ranging from 1.7 to 2.5 per 

 cent. This water is lost gradually with rising temperatures without any loss 

 of homogeneity and with very slight change in the optical properties. The 

 water is therefore not chemically combined, although the mineral in the pow- 

 dered state is not completely dehydrated under 900°. It is to be regarded as 

 dissolved water, and tremolite as a solid solution. A diopside from a meta- 

 morphosed limestone contained i per cent of water and behaved in practically 

 the same way, though presumably the diopside of eruptive rocks is anhydrous. 



The amphibole kupfiferite and a specimen of beryl contained respectively 

 3.8 per cent and 2.5 per cent of water, which thev lost very slowly at compar- 

 atively high temperatures (400° to 800°) and still retained their homogeneity. 

 With them, however, the loss of water appeared to progress so slowly at these 

 temperatures that the total water could not be driven ofif in anv reasonable 

 time. The beryl lost at the same rate for a long period, both in drv air and in 

 an atmosphere containing water vapor at the partial pressure of about 23 

 mm., even though this rate appeared to show that the mineral possessed a 

 vapor-pressure of only about 0.5 mm. of mercurv. The kupfferite showed a 

 similar behavior, but the fact that it suffered a secondarv change in composi- 

 tion at the higher temperatures (probably due to the absorption of oxvgen) 

 made this measurement less satisfactory. 



All these minerals show important points of resemblance with the zeolites 

 with which they may broadly be classed, but in one important particular thev 



