478 Obituary — Dr. Samuel Calvin. 



These cleavage and other lines are still more clearly marked near to 

 the margin, are eroded into and charged with decomposition-products, 

 mainly scales of gibbsite, but with some opaque white and dust-like 

 substances. As the junction is approached the larger felspar prisms 

 and the aggregates of smaller ones gradually break up into small 

 granular non-striated fragments lying in and surrounded by aggregates 

 of scales of gibbsite, interspersed with more or less opaque dust-like 

 substances. Many of the granules are eroded, and their contours 

 remind one of those of sugar crystals dissolving in water. Here and 

 there in the larger plates of felspar aggregates of scales of gibbsite 

 form inlets. 



The pyroxene masses in places are changed into aggregates of 

 < viridite ' or of chlorite, but more often the cleavages of otherwise 

 apparently unaltered augite are lined and filled with limonite. Nearer 

 to the margin of the diabase this latter condition steadily increases 

 until close to the contact of the rock and the laterite the masses of 

 augite are changed into reticulations of limonitic products with small 

 unaltered fragments of pyroxene. 



Where the rock is actually changing to laterite, all the masses of 

 its augite are altered into reticulations of limonitic oxides of iron 

 with few remnants of more or less unchanged pyroxene, and with 

 relatively few minute aggregates of scales of gibbsite and of dust-like 

 opaque products. 



The final change in the slices examined from felspars somewhat 

 corroded to aggregates of gibbsite in parts of them occupied a breadth 

 of less than -2 of one millimetre, whilst in places, especially where 

 the felspar lies in aggregates of small prisms, the change must be 

 described as abrupt. 



The distance between the apparently unaltered diabase and the 

 lateritic aggregate of limonite and gibbsite with few minute fragments 

 of unchanged felspar, some minute granules of secondary quartz, and 

 grains of ilmenite varies in the specimens examined from 1 - 6 millimetres 

 as a minimum to 39 millimetres, or to about one-seventh of an inch, 

 as a maximum. Thus the actual change is mainly, although not 

 entirely, a surface one, the alteration noticed along the cleavage and 

 other lines in the inner parts of the diabase being of very subordinate 

 importance to the superficial ones. 



J. B. Harrison. 

 Science and Agriculture Department, 

 Georgetown, Demerara, 



August 19, 1911. 



OBITUAET. 



SAMUEL CALVIN, M.A., LL.D. 

 Born February 2, 1840. Died April 17, 1911. 



Samuel Calvin was born in Wigtonshire, Scotland, on February 2, 

 1840. He went with his parents to America when he was 11 years 

 of age, and received his education at Lenox College, Iowa. When 

 he was 24 years old he enlisted in the Army and served for a few 

 months in the Civil War. He then became a teacher of science in 



