162 CARNEGIE INSTITUTION OF WASHINGTON. 



The needs of the group of scientific investigators are easiest to meet. 

 A simple collection of the principal facts, accompanied by a thorough 

 bibliography, will satisfy them, for they are already familiar with much 

 of the material. But a thorough bibliography is worse than useless to 

 some of the groups concerned. The petrologists, for example, desire 

 the new physical and chemical facts about silicates, not in the form in 

 which they were originally discovered, but interpreted in terms of the 

 forms with which a petrologist works, namely, the natural minerals and 

 rocks. The ceramic chemists and engineers, on the other hand, desire 

 the same facts freed from their burden of experimental and theoretical 

 proofs, just as in the case of the petrologist, but interpreted this time in 

 terms of technical products — porcelain and glaze, bricks and pottery, 

 refractories, and manufacturable glass. Last, and most important, 

 is the group made up of students in colleges and technical schools, 

 whose interest is in the future rather than in the present, and whose 

 needs are therefore the hardest of all to meet. They want all the 

 facts, for if history furnishes any guidance it is probable that the im- 

 portant facts and relations of the future will be drawn in part from the 

 unimportant facts of to-day. 



The effort has therefore been made to provide a reference book on 

 the facts and theories of the silicates which may find application alike 

 to the needs of the student of ceramics, of mineralogy, of petrology, 

 or of inorganic chemistry. 



The classification of the subject-matter cuts right across some of the 

 standard groupings of mineralogy, but is expected fully to justify itself 

 by its elasticity and by the new relations which can thus be brought 

 out. Silicate theory during the past fifty years has been too dependent 

 upon the analogies of organic chemistry, and sufficient use has not yet 

 been made, in silicate research, of the principles developed in recent 

 years by investigators in the field of physical chemistry. In the long 

 step forward now being taken in our knowledge of molecular and atomic 

 structure, investigators should draw very considerable aid from the 

 large body of facts already assembled by the mineralogists and other 

 students of silicate chemistry. 



It may be of interest to record the fact that with the forthcoming 

 publication by the War Department of Colonel Wright's book, "The 

 manufacture of optical glass and of optical systems" (reviewed on 

 page 174), the numbered publications on optical glass resulting from 

 the war activities of this Laboratory will reach forty. 



Brief reviews of the papers published by members of the Laboratory 

 staff during the current year will be found on the following pages: 



