190 
MR. 0. BARRINGTON BROWN AND PROFESSOR .T. W. .TUDD 
microscope, where necessary isolating and submitting to different physical and 
chemical tests their several constituent minerals. 
Specimens of the ruby-earths have been washed in the laboratory, and the minute 
fragments of minerals in them isolated by the use of heavy liquids. The particles 
thus obtained have been studied microscopically, various physical and chemical tests 
being applied for their identification. 
The collections of materials from the washings at the mines have proved to be of 
great value as a means of estimating the nature of the minerals present, and (in some 
cases) of the relative proportions of the different minerals occurring in these alluvial 
deposits. 
The limestones have been studied, not only by thin sections, but also by dissolving 
considerable quantities of them in acid, and separating the minerals left behind by 
the aid of heavy liquids. In this way it ha.s been possible to determine not only 
the several minerals present in the calcareous masses, but also the proportions which 
the carbonates bear to the silicates and other minerals scattered through them. 
In studying this series of rocks I have received the greatest assistance from the 
admirable work of Lacroix on the rocks of Ceylon and Southern India, and his 
comparisons of these with the pyroxene- and scapolite-rocks of other areas, such as 
Brittany, Central Europe, Spain, Algeria, Western Africa, Eastern Africa, Norway, 
Sweden, and the United States.* My studies of the rocks has also been facilitated 
by the receipt of numerous specimens from former students and correspondents ; in 
particular, I may mention valuable collections obtained by me from Mr. C. Barrington 
Brown and Mr. P. Bosworth Smith, from Ceylon and Southern India, and from the 
latter gentleman and from Mr. T. H. Holland, of the Geological Survey of India, 
from the Salem district; from Mr. Nason and Professor F. D. Adams I have received 
interesting examples of the pyroxene- and scapolite-roeks of the North American 
Continent; while to Mr. F. B. Mallet I am indebted for specimens from South 
Bewah, and for much valuable information concerning several Indian localities. 
In the task of working out these rocks I have been aided by several of my 
assistants in the Geological Laboratories of the Pcoyal College of Science, especially 
by Mr. T. W. Holland, F.G.S. (now of the Geological Survey of India, and the 
Presidency College, Calcutta); by Mr. G. W. Card, F.G.S. (now curator of the 
Geological Survey Museum, Sydney, N.S.W.) ; and by Mr. T. Barron. To another 
assistant, Mr. F. Chapman, I am also especially indebted for the great skill he has 
shown in making microscopic sections, often from very troublesome materials. 
The corundum-bearing rocks of Southern Asia appear to have a very wide distribu¬ 
tion, and, so far as they are known, to exhibit remarkably uniform characters. The 
# “ Contributions a l’etude des Gneiss a Pyroxene et des Roches a Wernerite,” par Alfred Lacroix. 
‘ Bull, de la Soc. Fr. de Mineralogie.’ April, 1889. A translation of the portions of this memoir 
relating to Ceylon and tire Salem district lias been made by Mr. F. R. Mallet, and published in the 
‘ Records of the Geological Surrey of India.,’ vol, 24, Plate 3, pp. 155-200. 
