GEOPHYSICAL RESEARCH — DAY. 229 



anticipate positive results, and so far no insurmountable difficulties 

 have been met with, nor has it been necessary for us to diminish the 

 standard of accuracy which has heretofore been maintained. 



It is interesting to note the continual cropping out of technical 

 problems at every stage of the process. The development of a pure 

 ferrous silicate has already been shown to involve the relation of 

 pure iron to its oxides and to reducing agents, while the study of 

 lime-silica mixtures is fundamental in the preparation of Portland 

 cement. Questions of technical interest in glass manufacture reap- 

 pear everywhere in handling silicate solutions. 



The laboratory has also another matter in hand upon which work 

 has been done at odd moments, but which is not yet far advanced, viz, 

 the study of change of volume of crystalline substances when passing 

 their melting-point — a question upon which positive experimental evi- 

 dence has only once been obtained. Some fifteen years ago Professor 

 Barus reached the conclusion, in his work upon natural diabase, that 

 the mineral in its solid state was about 3 per cent more dense than 

 the liquid at the melting temperature ; but there is still some question 

 as to whether this result may not have been influenced by under- 

 cooling during solidification. 



VISIT TO EUROPEAN LABORATORIES. 



Under an allotment of $600, payable from the present appropriation 

 and authorized in February last, Dr. Day visited the laboratories of 

 Europe in which mineral mixtures have been studied, during the 

 months of May, June, and July just past. The objects of the trip 

 were two : First, to gather technical information which might be of 

 service in the equipment of the laboratory or in carrying out measure- 

 ments of the high order of accuracy which we have adopted for this 

 work ; second, in the interest of progress in this general field, to 

 arrange, in so far as might prove feasible, to divide the efforts of those 

 engaged in this work, so as to avoid duplication. 



The fundamental reason for the trip was an economic one. It is 

 very desirable to avoid unnecessary or unsuccessful experiments at 

 high temperatures whenever it is possible to do so, on account of the 

 waste of resources involved, and of course equall) 7 undesirable that 

 two or three laboratories should go over practically the same ground. 



A great deal of technical information upon special points was ob- 

 tained, which was most cheerfully given and will be of considerable 

 benefit in the work of the coming year. It also proved possible to 

 arrange for a moderate amount of cooperation with other scientists, 



