698 EEPORT— 1900. 



The specific beat of CO, is found to rise regularly with the temperature. Varia- 

 tions in the pressure of the gas produce slight variations in the specific heat. 



The foUowinir values have been obtained by reducing the observed values bv 

 means of Joly's formula to the same pressure : — 



Initial Temperature Final Temperature Specific Heat reduced to 



Pressure of 100 Atmos. 

 115' 1G° -2000 



118° 17° -2004 



192° 17°-5 -2092 



298° 21° -2884: 



398° 21° -3565 



The authors propose to determine the specific heat of nitrogen and of argon 

 under the same conditions -u-ith the same apparatus. 



2. Interim Rejwrt on the Nature of Alloys. 



3. Report on the Chemical Comjwunds contained in Alloys. By F. H. 

 Neville, F.H.S.—See Reports, p. 131. 



4. 0)1 the Mutual delations of Iron, Fhosphortts, and Carbon vjhen 

 together in Cast Iron and Steel. By J. E. Stead. 



5. The Crystalline Structure of Metals} By J. A.-EwiNG, F.E.S., Professor 

 of Mechanism, and Ajjplied Mechanics in the University of C amhridge ; 

 and Walter Rosenhain, B.A., St. John's College, Cambridge, 1851 

 Exhibition Commissioner's Research Scholar, University of Melbourne. 



The paper describes the results arrived at by the authors in investigating the 

 effects produced upon the micro-structure of metals by (1) plastic strain, and by 

 (2) exposure of strained metal to moderate temperatures. After describing and 

 illustrating the well-known characteristics of crystalline structure in metals as 

 revealed by the microscope, the authors show that plastic strain is accompanied 

 by the appearance of minute steps on a surface of the metal which had been plane 

 polished before the application of the strain. When viewed under the microscope 

 these steps appear as black lines under normally incident light, but they appear as 

 bright bands when oblique light of suitable incidence is used. Their observations 

 lead the authors to conclude that metals yield under plastic strain by the slipping 

 of the component parts of each crystal along definite cleavage or gliding plane. 

 The steps in the surface being a consequence of these slips, the authors have called 

 them 'slip-bands.' Further evidence leads the authors to conclude that plastic 

 strain in metals occurs without loss of crystalline character, the crystals as a whole 

 accommodating themselves to new shapes and positions by the slipping of their 

 elements, with the result that the crystalline structure is preserved even when the 

 material as a whole undergoes much deformation. 



The use of slip-bands as a means of microscopic observation is also described 

 and illustrated, more particularly with reference to the occurrence and formation 

 of twin-crystals in copper, gold, nickel, lead, and other metals. Slip-bands are also 

 illustrated in various kinds of iron and steel, nickel, zinc, tin, cadmium, lead, silver, 

 gold, bismuth, and some alloys, the magnifications varying from 40 to 1,000 

 diameters, 



' For other accounts of these researches see papers by the same authors, Proc. 

 Boy. Soc, March IG and May 18. 1890, May 31, 1900, and riul. Trans., vol, A, 1900, 

 and vol. A, 1901. 



