670 



SCIENCE. 



[N. S. Vol. XXIII. No. 591. 



looking about for the best university or li- 

 brai-y in whicb to deposit their own scientific 

 collections. If the wants of our universi- 

 ties and observatories and research stations 

 could be fully made known, through the col- 

 umns of Science, they would find a ready 

 response on the part of individuals who have 

 been profiting by the generous distribution of 

 expensive volumes during many years past. 

 Such volumes, whether published by the gov- 

 ernment or by societies, are, as it were, loaned 

 in trust to past recipients, who, having bene- 

 fited by them, should now in turn pass them 

 on to others, rather than hoard them, or sell 

 them as merchandise. 



Cleveland Abbe. 



the mental development op individuals. 



To THE Editor of Science : I wish to learn 

 at what 'age, under what circumstances and to 

 what extent people of different climes, races, 

 civilizations and temperaments have changed 

 their views as to whence we came, whither we 

 go, and what we are here for. Any statement, 

 elaborate or short, regarding an individual's 

 mental development will be a welcome contri- 

 bution to a proposed ' Natural History of the 

 Thinker.' I have been obliged to thus appeal 

 to my contemporaries because autobiographical 

 documents so far extant do not yield enough 

 accurate descriptions of the inner life. To 

 illustrate my purpose, I beg to refer to my 

 article on ' The Interpretation of a System 

 from the Point of View of Developmental 

 Psychology,' in the Journal of Philosophy , 

 Psychology and Scientific Methods, Febru- 

 ary 15. 



Edwin Tausch. 



Ohio University, Athens, O. 



SPECIAL ARTICLES. 



QUARTZ GLASS. 



Pure quartz when melted down to a glass 

 has three properties which make it of immense 

 value in the chemical and physical laboratory, 

 and were it not for the technical difficulties 

 attending its production, it would certainly 

 displace ordinary glass wherever a transparent 

 medium capable of withstanding heat is re- 



quired. It expands less than one tenth as 

 much as common glass when heated ; it can 

 be heated to 1,000° C. without softening; and 

 finally, it transmits ultraviolet light freely. 



It has not proved easy to make quartz glass, 

 even in small quantities in the laboratory. 

 Quartz is one of those peculiar minerals' 

 which show no sharp melting temperature, 

 but soften very gradually, and when pure, 

 never become thin liquids, even at the tem- 

 perature of the electric arc. Furthennore, 

 quartz begins to vaporize rapidly in air at 

 about the temperature of melting platinum, 

 while it is still much too viscous to release 

 the included bubbles. A mass of quartz frag- 

 ments, when melted in air in the electric fur- 

 nace, comes out resembling solidified sea-foam 

 or volcanic pumice. It is quite opaque, dirty 

 and useless for mechanical or optical purposes, 

 and very persistent efforts in a number of 

 laboratories have so far failed to produce a 

 clear product except from single fragments 

 treated individually. Small globules of glass 

 can be obtained from single crystals, pieced 

 together in the oxyhydrogen flame, and blown 

 into thin quartz glass vessels such as are now 

 in quite common use. Discs suitable for 

 small lenses have also been obtained at Jena 

 by heating small clear crystals with such 

 rapidity as to produce a thin enclosing film 

 of liquid before cracks develop in the body of 

 the crystal, thereby preventing the entrance 

 and subsequent enclosure of air. It is, of 

 course, plain that such devices can have but 

 limited usefulness. We must somehow man- 

 age to melt larger masses of random fragments 

 to a clear glass before the technical problem 

 can be regarded as solved. 



This problem is somewhat outside the proper 

 scope of the Geophysical Laboratory, but our 

 plant is perhaps better adapted to its solution 

 than most others, and the demand for clear 

 quartz glass is so general that it seemed best 

 to spend a limited time in an effort to fijid 

 the difficulty and to try to ascertain the direc- 

 tion in which the solution lies. No effort at 

 refinement of method has yet been made. 



^ See Day and Allen, ' The Isomorphism and 

 Thermal Properties of the Feldspars,' Publ. 31, 

 Carnegie Institution. 



