L. H. Adams

The annealing of glass as a physical problem

Abstract The fundamental principles underlying the annealing of glass and the present state of knowledge concerning changes in the nature of glass during heating and cooling are briefly reviewed. Emphasis is placed on the fact that a quantitative explanation of the formation and removal of strain in glass, and a precise determination of the requisite conditions for any desired degree of annealing, may be obtained on a purely mechanical basis, without consideration of the internal constitution of materials in the vitreous state. Annealing Practice. —An improvement in the definition of annealing time (made feasible by the relatively great speed with which large strains are released) allows a considerable simplification in the determination of the proper procedure for annealing. As an illustration, the procedure for annealing a disk of Pyrex glass, 200 inches in diameter, is given. The best conditions for annealing, when for any reason the temperature must be above or below the most favorable temperature, are also discussed. Effect of Internal Stresses on Density. —It is demonstrated that internal stresses can have no effect on the total volume or on the average density of a block of glass. The stresses may cause a deficiency in density of the interior portion and an excess near the outside, but the mean density of any large or small piece is exactly the same as if the glass of any large or small piece is exactly the same as if the glass were free from stress. Although unannealed glass may have an abnormally low density, the stresses themselves have nothing to do with this effect. The Vitreous State. —The anomalies of glass in the annealing range, the relation between viscosity and rigidity, the physical basis of the rate of release of strain, and the possibility that glass at low temperatures may have a finite strength, are discussed. Although a lack of data prevents the drawing of any positive conclusions, nevertheless the state of aggregation of glass is a problem of very great interest. It appears that more attention should be given to the physico-chemical side of the problem; but it is essential not to confuse phenomena that involve the internal constitution of glass with those that do not.

Observations on the Daubrée Experiment and Capillarity in Relation to Certain Geological Speculations

Those who believe that meteoric waters are an important factor in the production of the phenomena of vulcanism have always met with difficulty in devising a means by which surface waters could reach deep-seated and highly heated regions. This difficulty they have, as they believed, obviated by instancing an experiment made by Daubree on the passage of water through a porous sandstone against a certain excess counter pressure. That this experiment has no bearing on the question at issue has already been pointed out more than once; but this has apparently not attracted the attention of those who wish to believe in its applicability as a proof of the possibility of introducing accessions of meteoric water into the magma. Accordingly we propose to discuss this experiment and the laws governing capillary processes (of which it is an example); and we endeavor to point out the limitations which must be borne in mind when capillary effects are adduced as important factors in the production of geological phenomena such as vulcanism.

Twenty‐Third Award of the William Bowie Medal

Keith Edward Bullen has made outstanding contributions to geophysical science by his researches on seismology and the nature of the Earths interior. He was born in Auckland, New Zealand, in 1906, and attended the University of New Zealand, where he was granted the degrees of M.A. (with 1st Class Honors) in Mathematics, and B.Sc. in Physics. In 1927 he was appointed Lecturer in Mathematics at Auckland University College. Dr. Bullens interest in seismology arose especially through the occurrence in 1931 of New Zealands worst earthquake, and his meeting with Sir Harold Jeffreys in Cambridge, England, the same year. On leave of absence from Auckland, he spent two years as a research student at St. Johns College, Cambridge, working with Jeffreys. Subsequently the University of Cambridge recognized his ability in Earth science by awarding him the Ph.D. degree and later the Sc.D. degree.