2 
MESSRS. C. T. HEYCOCK AND E. H. NEVILLE ON 
two lines of research, and the exact nature ol this group of alloys remained very 
obscure. 
The ingots of alloy which we studied at first had been allowed to cool somewhat 
slowly and spontaneously in the furnace, so that there had been no sudden chill or 
alteration in the rate of cooling. Polished and etched sections of these ingots were 
found to contain very varied and complicated patterns that sometimes appeared to 
have no connection with the singularities of the freezing-point curve. For example, 
a tin-rich crystallisation which appeared to he primary, was found to increase to a 
maximnm amount as we descended a branch of the curve, and in more than one 
region undeniable primary crystals which stood out in relief on the outside of the 
ingots were found, when polished half-through, to he full of smaller and quite 
different crystals. In fact, it became evident that the final patterns we were 
examining were of the nature of a palimpsest in which several different records were 
superposed, some of these being due to recrystalhsations that had taken place aftei 
solidification. Two other considerations pointed to the same conclusion, the first was 
derived from the very valuable cooling curves, published by Roberts-Austen and 
Stanseield in 1895, which revealed the fact that far lielow the temperature of 
solidification considerable evolutions of heat occurred in the alloys as they cooled. 
The second was derived from Professor Poozeboom’s paper on the “ Solidification of 
Mixed Crystals of Two Substances,” published in tlie ‘ Zeitschrift fiir Physikalische 
Chemie,’ of December, 1899. These two researches have been respectively the 
experimental and the theoretical basis from which the present work has grown, and 
tlie possibilities of interpretation which they promised have induced us to make a 
much more serious study of the bronzes than we originally intended. 
It soon Ijecame clear that in order to understand the nature of the alloys it was 
essential to examine their structure at all temperatures, from the freezing-point 
downwards. We therefore adopted the plan of chilling small ingots at selected 
temperatures. We hoped that, as in the case of steel, the structure existing at a 
particular temperature would he so far stereotyped by the sudden co<^hng of the chill 
as to be recognisable under the microscope. This hope has been to a very large 
extent justified, most of the doubtful points as to the nature of the bionzes ha\ing 
been cleared up by the evidence derived from the chilled ingots. In February, 1901, 
we published in the * Proceedings of the Iloyal Society a short paper desci ibing the 
method, and gave some photomici'ographs illustrating the extraordinary changes that 
a solid alloy can undergo as it cools, and in December, 1901, we read before the 
Iioyal Society another short paper on the same subject. The latter paper contained 
a diagram giving a complete view of the conclusions we had arrived at, concerning 
the nature of the copper-tin alloys. The paper was published in the ‘ Proceedings,’ 
vol. G9. The jihotomicrographs, which formed an important part of the evidence for 
the truth of the diagram, were exhibited by one of us when the papei vas lead, but 
were not included m the paper. I he present paper does not represent any gieat 
