PROCEEDINGS OP THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
223 
He was also much pleased with all the other departments. 
In a subsequent letter to Colonel Drummond Hay, Pro¬ 
fessor Flower expresses the hope that we will be able to con¬ 
tinue and extend the Museum on the same lines as we have 
begun. The other naturalist to whom I referred is the well- 
known ornithologist and explorer of the natural history of 
Palestine, Canon Tristram, of Durham. He spent a whole 
afternoon in the Museum with our Curator, and his opinion 
is as follows:—" Though small, it is my beau-ideal of what a 
local museum should be; and by no other arrangement could 
you so interest and instruct visitors who wish to learn some¬ 
thing of the local fauna and flora." The collection of nests 
—crushed together as they are from want of space—was 
much admired by Canon Tristram, who in fact had not 
a single unfavourable criticism to make in any department. 
I may add that, as imitation is said to be the sincerest 
flattery, Professor Trail is paying a great compliment to 
our Museum by getting up one on the same lines in Aber¬ 
deen. 
With these commendations (and many others might be 
added) of the result of our labours, we ought to be encour¬ 
aged to endeavour to continue the good work. It is, un¬ 
fortunately, the case that the limited funds that we had at 
our disposal have now been exhausted, and we cannot, 
perhaps, entertain very sanguine hopes of raising more just 
at present. But what has been done in the past may be 
done again in the future; and, therefore, I think we should 
constantly keep in mind the necessity of not only main¬ 
taining, but of extending, the Museum. Retaining this 
always—in season and out of season—in view, we cannot 
fail to be succeseful in reaching our goal. 
The following paper was read : — 
“ The Fossil Diatoms of the Tay Basin." By Dr Trotter. 
It is not my intention to-night so much to treat of the diatoms 
of the Tay, as to supplement my former paper with some ac¬ 
count of the alluvial beds of the Perth Basin, and of the various 
microscopic objects—chiefly diatoms-found in them. The 
Perth Basin, as you are all aware, is a deep depression, near the 
south-eastern extremity of the great band of the Old Red Sand¬ 
stone, stretching from S.W. to N.E., and forming in our own 
neighbourhood the well-known Howe of Strathmore. The 
deepest part is where the Tay passes out of it on the S.E. between 
the lofty basaltic rocks of Kinnoull Hill and Monereiffe Hill. 
It gradually shoals towards the Almond, and is closed on the 
north by the high land in the neighbourhood of Luncarty. 
Along part of its western side an ancient shore is still very dis¬ 
tinctly visible in several places (the sand-hills forming its margin 
being in some places extensi vely excavated for building purposes), 
and is very conspicuous near the residence of the late Sheriff 
Barclay at Craigie, at the Craigie Public School, and at Wells- 
hill on the west, and at Comely Bank on the east. 
It becomes an interesting question whether this basin was 
originally an inland lake, which had gradually worn a way 
through the hard rocks of the Sidlaws, and emptied its waters 
into the estuary beyond, either by the opening out of a chasm at 
the same place, or by the gradual wearing of glacier ice, the 
action of which has left unmistakable impressions on all the 
rock surfaces around ; or whether it was simply a land-locked 
arm of the sea, which gradually became silted up by the deposi¬ 
tion of alluvial mud from the River Tay. If the latter, it 
becomes necessary to consider whether the clay of this basin 
could have been deposited in an arm of our present sea, or 
whether it is imperative to conclude that when the deposition 
occurred, the land was at a lower level than at present. 
At the Friarton Hole, just below the harbour, there are ex¬ 
posed a number of strata of a red clay, very soft and plastic, and 
of unknown depth, with the appearance of having become 
almost rock. This clay appears in various places in the 
basin, sometimes red sometimes yellow, but beariug similar 
characters everywhere, and always seeming to be the basis on 
which the other deposits rest. It is very finely seen in a deep 
pool at the lower end of what is called the “ Woody Island,’’ 
nearly opposite Scone Palace. 1 have repeatedly examined por¬ 
tions of this clay from various places, but in no case have I de¬ 
tected any organism in it. It is as barren of organic remains as 
a piece of granite, and gives a different series of colours with the 
polariscope, appearing to consist in great part of silicate of 
alumina. 
It is difficult to conceive of any body of still water existing 
long enough to deposit repeated layers of fine mud over such a 
large extent of bottom, without the presence of even the sim¬ 
plest organisms; but careful investigation has so far failed to re¬ 
veal anything of the kind. Lying immediately above this, how¬ 
ever, is a clay, almost similar in general appearance, though 
of a bluish colour ; but under the microscope its appearance is 
very different, for it is full of pieces of silica of various sizes, 
and in addition contains numerous organic remains. 
The commonest of these are what are believed to be sponge 
spicules. Spongiolithis acicularis is very plentiful, a piece of 
clay twice the size of a pin’s head—a size suitable for examina¬ 
tion-containing on an average twelve entire specimens, besides 
numerous broken fragments. These organisms, which look like 
the sharp halves of two needles joined together at an angle of from 
5 deg. to 10 deg., are composed of silica, with a tubular cavity 
extending through the whole length, and opening with an oval 
aperture almost at the end. They show no markings of any 
kind, even with the highest powers. Some authorities consider 
them to he Diatoms, while others think them Sponge Spicules. 
They are not uncommon among the live diatoms of the Tay, 
and appear to move about like the others, but I have failed to 
colour them with any of the staius which colour the diatoms. 
At the waterfall at Craighall, one of the commonest diatoms, 
about which there is no doubt, exactly resembles these, except 
that there is a small protuberance in the angle, and it is about 
the size of the smallest of the spicules. Whether sponge spicules 
