416 Progress in Science. (July, 
Battle) was estimated at 400 feet, so that no doubt the bottom will soon be 
reached. 
The discovery of beds of gypsum between the depths of roo and 180 feet, in 
the Purbeck Beds, and which would probably never have been known but for 
this scientific enterprise, have been already sought for and found at Archer’s 
Wood, on the estate of the Earl of Ashburnham. As Mr. Willett observes, 
it is a matter of congratulation that by this discovery there has been developed 
for the county a new industry, which promises to be highly remunerative to all 
parties. 
Geological Society of London.—This Society has just commenced the re- 
moval of its Library and Collections from Somerset House to the new apart- 
ments prepared at Burlington House. The superior accommodation, which 
was more especially wanted to display the large collections of rocks and 
fossils, will no doubt be appreciated by the Members. 
The late Professor Phillips\—The scientific world at large, and geologists 
particularly, have sustained a great loss in the death of Professor Phillips. 
Few men have possessed so wide a range of knowledge, and no one has done 
more to further the advance of Geology, by special work in all its departments, 
than John Phillips. He was born in 1800, and, being early left an orphan, 
was adopted by his uncle, William Smith, the Father of English Geology. 
From his sixteenth year he accompanied Smith in his various geological 
journeys across England, and was thus early trained to accurate observation 
in the field by his uncle, whose early teachings directed the whole course of 
his life. In 1825 he was appointed Keeper to the Museum of the Yorkshire 
Philosophical Society, a post which he held until 1840, when he was appointed 
to the Geologica} Survey under De la Beche, and not only did much detailed 
work in the field, but described the Palzozoic fossils collected in West Somer- 
set, Devon, and Cornwall. In 1834 Mr. Phillips was elected to the Chair of 
Geology in King’s College, London; in 1844 he was appointed Professor of 
Geology in the University of Dublin; and in 1853 he was called to the duties 
of Reader in Geology in the University of Oxford. In 1859 he was elected 
President of the Geological Society of London, and in 1864 President of the 
British Association, of which latter body he was one of the founders. The 
writings of Professor Phillips were very numerous. At the time of his death 
he was preparing a new edition of his ‘* Geology of Yorkshire.”” He died on 
the 24th of April, having met with a severe accident on the previous day, 
falling headlong down a flight of stone stairs. 
PHYSICS. 
Microscopy.—Mr. F. H. Wenham has described* a more accurate mode of 
measuring the angular aperture of microscopical objectives than that hitherto 
practised. The angle of aperture of an object-glass is taken from the focal 
point through which the rays must pass for all degrees. Those entering at 
other angles within the plane of focus will give a false indication, from diffused 
light forming no image. Mr. Wenham employsa movable slit of thin platinum- 
foil so mounted as to be secure from damage from accidental contaé& with the 
objeé-glass, or otherwise. This instrument is placed upon the stage of the 
microscope, with the body horizontal, and set on a wooden turntable about 
to inches in diameter, having its edge divided into degrees. The object-glass 
to be measured 1s focussed on the glass surface, and the slit adjusted so that 
its two edges just appear in the field of view, and by the rotation of the turn- 
table the degrees of aperture are read off. The microscope should have a thin 
stage, so that the rays may not be cut off at extreme angles. Measurements 
taken with these precautions come out much lower than those by the ordinary 
mode, as the image-forming rays alone enter into the objective. Mr. Wenham 
considers the large front glasses of many objectives not only useless but 
injurious, and the performance of such glasses is much improved by turning 
away the front, so as to only leave the actual working portion to receive the 
* Monthly Microscopical Journal, vol. x1., p. 198. 
