PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
193 
but yesterday, and they will endure as perfect as 
ever long after the name of the Fair City is forgotten. 
I have no doubt many of our members have observed 
a series of sandy ridges extending, with various inter¬ 
ruptions, almost round the basin of which Perth may 
be considered the centre. These sandhills are very con¬ 
spicuous at High Craigie, where they have been exten¬ 
sively used for building purposes. They are also very 
prominent at the head of Friar Street, in the New Town, 
the new Board School being built on one of them. On the 
eastern side of the town they are well seen atKincarrathie 
and Pitcullen, and on both sides of the city they maintained 
an elevation of about 50 feet above the present sea-level, 
and mark the shores of a former arm of the sea, very much 
resembling some of the West Highland marine lochs. At 
about 10 to 15 feet lower than those sandhills there is in 
several places an extensive bed of brick clay, the former 
sea-bottom, which, in several spots, sloped gradually up so 
as to be left dry at low water. On the clay of the deeper 
parts of this ancient bottom being examined with the mi¬ 
croscope, very few diatoms are found, but the silicious 
spicules of marine sponges are found in great numbers,—a 
portion of clay about the size of a pinhead containing on 
an average about ten of them. These, I need scarcely say, 
could get there only by the sponges living and dying there, 
or their remains having been washed there by the waters 
of the ocean. Those of you who have been at seaside places 
where the shores were flat and marshy, will be familiar 
with what are called inks or merse-holes—little pools in the 
salt marshes, which do not fill up with clay, and into 
which the sea flows regularly. Such places once 
existed on the west side of Perth, and it is from one 
of these ancient inks that I got the old world diatoms. 
At the top of the old High Street, near the site of St 
Catherine’s Chapel, a drain was cut for some new buildings 
now being erected, and the drain passed through two de¬ 
posits of dark blue clay, quite different in appearance 
from the yellowish clay by which they were surrounded. 
This clay so much resembled the clay beside my native 
village that I took portions of it and the yellow clay home, 
and on examination I found the blue clay teeming with 
diatoms altogether different from those of the Tay, and, 
with two exceptions, exclusively marine or brackish water 
forms, while the yellow clay contained a few of the 
same diatoms and very numerous sponge spicules. The 
clay at different depths contained different forms, 
as if the life of each particular kind depended on some 
certain depth of water. A short time after this I was on 
the shores of the Solway Firth, and found the inks 
there at the present day containing precisely similar 
diatoms—some exactly alike and others slightly modified. 
The city of Perth, therefore, is built on beds of clay 
teeming with millions of these interesting objects, which, 
though trivial and unimportant in themselves, are valuable 
and interesting to the student of natural history, as point¬ 
ing out in unmistakable terms some of the great geological 
changes to which our country has been subjected, and also 
by indicating to us the inconceivable beneficence of Divine 
Providence, in bestowing so much beauty in form and 
ornamentation on objects so minute that man with unaided 
eye could never have so much as suspected their existence 
—objects which, though so minute and so low in the scale 
of creation, existed in innumerable forms long before man 
came into being, while their silicious skeletons will last as 
perfect as ever long after man has disappeared from the 
earth. 
A large number of specimens were shown by the aid of 
the microscope. 
January 22nd, 1885. 
CONVERSAZIONE. 
A conversazione was held in the Museum buildings in 
Tay Street, at which a large number of the members and 
their friends were present. The chief attraction was the 
Museum, where the newly-arranged cases were inspected 
with great interest. The cases of Perthshire birds, and 
particularly that containing the nests and eggs, were 
especially admired. Some of the members who have taken 
a more active part in the arrangement of the various col¬ 
lections explained the general plan of the Museum, and 
drew attention to the points of special interest. In the 
Lecture-Room a number of microscopes were on view in 
charge of members, who exhibited collections of objects in 
all departments of natural science. Among the more at¬ 
tractive of these were a number of living diatoms from the 
River Tay, as well as other forms of microscopic plant and 
animal life, and some beautiful sections of the crystalline 
rocks of the neighbourhood shown by aid of the polaris- 
cope. A novel aid to microscope work was exhibited by 
Mr J. Campbell, optician, in the form of an exeeeedingly 
small electric light, known as the “ midget ” lamp, which 
