Henry Clifton Sorby. Ixii 
instrument to a large number of different substances, and published some forty 
papers in different branches of scientific enquiry wherein colour plays a part, 
such as the pigments in human hair, birds’ feathers, the shells of birds’ eggs, 
and the colouring matter in almost every group of plants. One of the 
practical applications of this invention to which its author attached 
importance was the detection of blood-stains. He stated that “as small a 
quantity as a hundredth part of a grain may be detected under circumstances 
in which it would be utterly impossible to recognise it either microscopically 
_ or chemically even if present in much larger amount.” It is interesting to 
note that many long years after these researches were made, when he lay 
on what proved to be his death-bed, he returned to this subject and collected 
some of his notes on experiments upon the colouring matters of plants, 
which he sent in the form of a communication to ‘Nature ’—the last paper 
which he published.* 
After the year 1879 Sorby spent five months of every year on board 
his yacht chiefly among the waters that surround and penetrate the low 
coast line of the south and east of England. Having no rocks to notice in this 
region, he was led to enter new fields of enquiry wherein he manifested the 
same mental activity and ingenious mechanical resourcefulness. Meteorological 
changes engaged much of his attention. He wrote on the colour of the 
clouds, sky, and sea, and on forecasts of the weather as deduced from the 
rainfall and changes in the barometer. For many years he continued to 
take observations of the temperature of the estuaries and more open waters. 
In 1882 he spent seven hours a day for 240 days in studying the Thames 
in connection with the enquiries made by the Royal Commission on the 
Drainage of London. He applied the microscope to the detection of sewage- 
contamination and of the purifying influence of minute animals and plants. 
His numerous researches on these and other subjects enabled him to lay 
before the Commission a large mass of important evidence which he believed 
had considerable influence on the findings in their Report. 
At frequent intervals he published accounts of the scientific results of 
his yachting cruises. These were usually communicated to the Sheffield 
Literary and Philosophical Society, sometimes to the ‘Essex Naturalist.’ 
More detailed observations on some of the groups of animals he collected at 
sea were now and then sent to the Linnean Society. But perhaps the most 
interesting and memorable outcome of these cruises was the ingenious 
methods which he devised and perfected for preserving even the most 
perishable forms of marine life and exhibiting them as permanent prepara- 
tions or as effective lantern-slides. At the soirées of the Royal Society in 1898 
and 1899, he exhibited some of these preparations which attracted much 
attention from the perfection with which the internal structure of the 
animals was revealed by them. He had found by experiment that a great 
variety of modes of treatment for different animals was required to secure 
the best results. Excellent transparent lantern-slides of some forms were 
* ‘Nature,’ January 16, 1908, p. 260. 
