NOTES. 95
shown what a careful and exact experimenter Dr. Gilbert was, but proved con-
clusively his title to be regarded as the father of the exact methods of physical
research. The names of Boyle, Otto von Guericke, Sir Isaac Newton, and
Stephen Grey were well known, and doubtless these men were inspired in their
work by the labours of Dr. Gilbert, though not till about one hundred years
after his magnificent researches in magnetism and electricity. In concluding,
Mr. Varley said he would like to point out that next December would complete
the centenary of Cavendish's celebrated discovery of the production of nitric acid
by the electric spark, which he experimentally proved before the Royal Society
in December, 1787.
Professor Thompson briefly returned thanks, and the meeting ended with the
usual conversazione.
Silene otites in Essex.—As I am responsible for the introduction of Silene
otites into Essex, perhaps I had better make a few remarks on the subject.
In July, 1868, the Rev. A. H. Wratislaw, who then lived at Bury St. Edmunds,
captured a specimen of Dianthaecia irregularis, a beautiful moth quite new to
Britain, at Tuddenham, and finding afterwards that the larva fed upon this species
of Silent, he invited me to join him at Tuddenham, and do some collecting.
When there, I noticed that the plant was growing luxuriantly on the walls of the
churchyard; and thinking it would probably fail to thrive in my own garden, I
took the precaution of sowing seed on the walls of my brother's garden, on
Colchester Castle, and on the Roman wall near by. I also gave some seed to
Mr. Laver, who informs me that he too sowed some on Colchester Castle, as well
as on a sandy bank at Layer-de-la-Haye. The seed sown in the open in my own
garden produced many plants which only lived for a time, and that sown at Layer-
de-la-Haye apparently failed to germinate; but there was a fine crop of plants
for several years on the garden walls, and a few stunted ones appeared on the
Castle and one the Roman wall. My object was to have a supply of fresh food at
hand, for the "Brech" district is not easily accessible from Colchester ; moreover
as most of the larvae, I found, were ichneumoned, I hoped by enclosing bred
specimens on the growing plant in muslin sleeves I might obtain fertile eggs, and
rear the larvae without any risk of having them stung. But in this instance the
plan I have found successful in many other cases did not answer, though the
garden walls yielded a good supply of food until one of my brother's men took it
into his head that they would look much better without "them nasty weeds"
growing on them, and accordingly uprooted all the Silene. A few plants have since
sprung up from seeds sown naturally, and probably many more may appear in the
course of time. There is not the smallest reason for supposing that the plant is
indigenous to this part of Essex, and nobody who has seen it growing naturally
would dream of finding it here, as our local conditions would be altogether
adverse.—W. H. Harwood, Colchester, March 30th, 1887.
The Lexden Subsidence.—My friend Mr. F. Rutley has just written to me
enclosing his original note on the Lexden subsidence which he has lately found
among some papers. It runs as follows : "A remarkable landslip, though on a
very small scale, occurred some time since in a field at Lexden, near Colchester.
A piece of ground from 18 to 20 ft. in diameter, and perfectly circular, has sub-
sided about 12 ft. below the surface of the field. The soil is an upper tertiary
gravel. No fossils are discernible in it." Below these remarks is the original of
the drawing given on page 2 of the Essex Naturalist (Fig. 2). Mr. Rutley
adds : "The measurements on it seem to fit in better with those of Mr. Wire and
the "Essex Standard" than those given by the Rev. Osmond Fisher. I must
have overlooked them when writing my letter criticising his article." In Mr. Rut-
ley's letter in the "Geological Magazine" no measurements are given. Thus we
now have a marked agreement on the part of three out of four observers as to the
size and shape of the Lexden hole.—T. V. Holmes, F.G.S., March 28th, 1887.