THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [February 11,1871\ 
G4S 
are about as far belcnv the Silurian in geological 
order, and certainly in the time that must have 
elapsed between their formation, as the Silurian 
rocks are below the present time. The oldest pre¬ 
viously known would come about the middle of the 
series. And when we consider that the older strata 
below are much harder, and must have taken a 
much longer time to form, the probability is that 
the lapse of time between the two must have been 
many times as great. The structure of this forma¬ 
tion is that which is known as serpentine limestone. 
Serpentine is a silicate of magnesia, and limestone 
is carbonate of lime. Serpentine marble is com¬ 
posed of a series of alternate laminae of carbonate of 
lime and green serpentine. The existence of this 
regular structure and this alternation of carbonate of 
lime and of serpentine impressed upon Sir William 
Logan the belief that it had an organic origin; but 
for a long time no specimens were found that yielded 
any evidence of this origin. About six or seven 
years ago, however, specimens were found which 
were examined by my Mend Dr. Dawson, Principal 
of M‘Gill College, Montreal, a most excellent micro - 
scopist and palaeontologist. He had a knowledge of 
my own researches in foraminifera, and was well 
acquainted with the treatise which I published on 
this subject some years ago, and I had chanced to 
send him a year or two previously some of my own 
sections and microscopic objects, which happened to 
be just what was required to give him the clue to 
the interpretation of these stratifications. In mak¬ 
ing sections of this stratum, he found distinct evi¬ 
dence in the calcareous layers of shelly structure. 
Here is a diagram, showing what the structure 
would be if it were possible to dissolve out the ser¬ 
pentine, and leave only the calcareous layers. It 
has just the appearance of nummulites, with curious 
extensions into the solid layers between them, and 
these extensions are filled with prolongations of 
internal serpentine. In another diagram you see 
the ramifications of the serpentine which occupies 
these extensions. This is an ideal drawing, be¬ 
cause we cannot dissolve away the serpentine and 
leave the carbonate of lime, but we can dissolve 
the carbonate of lime very easily and leave the 
serpentine. We thus get an internal cast or 
mould, showing the or'ginal form of the body which 
filled it. 
The key to all this is furnished by the discovery 
which was made some years ago by Professor 
Ehrenberg, that the greensands of various geolo¬ 
gical periods are distinctly composed, in great part, 
of the internal casts of foraminifera. There, for 
instance, is the bod} r of a Globigerina. Supposing 
that body, when dead and decaying, becomes entirely 
replaced by a green silicate; then dissolve away 
the Globigerina, and you will get a little mass 
exactly resembling the Globigerina in green silicate. 
That is exactly lvhat is found in the green sand¬ 
stone, and that process is going on at the present 
time. The examination of dredgings in different 
parts has shown that this process is going on at the 
bottom of the sea at the present time. Only a few 
months ago my friend Captain Spratt, who executed 
some years ago important dredgings in the Aegean 
Sea, placed in my hand some foraminiferous sand, 
and certainly the indications I saw in it led me to 
suspect that this change had taken place in many 
foraminifera. I put them into very dilute acid, and 
got a most perfect and beautiful series of internal 
casts, exactly corresponding with various forms 
which have already been found in the greensand. 
That gives the clue to the interpretation of this forma¬ 
tion. We have a calcareous shell in the living state, 
with all the cavities filled with sarcode, and one 
chamber budding off from another continuously, not 
like the Globigerina, having a certain regular plan 
and then ceasing, but growing by continuous exten¬ 
sion as corals do in making a coral reef. This 
chamber is filled with serpentine, which extends also 
into the minute peculiar cells which form what I 
call the nummuline layer. When we dissolve away 
the carbonate of lime, w r e leave here a set of little 
needles of serpentine, standing up side by side, or 
sometimes passing off into a brusli-like form; and 
sometimes a smooth layer is formed by the smooth 
ends of the little fasciculi of silicate, just like the 
pile of velvet. But in particular parts we find that 
a number of these tubes run together and form 
pencil-like brushes that exactly correspond with 
what have been found in recent shells of the same- 
kind. There is, in fact, no point in the structure 
of this Eozodn, which is so called, as indicating the 
dawn of life, which does not find its parallel in 
recent foraminifera. Having examined into the 
matter, I have come to the conclusion that Dr. 
Dawson was perfectly right in the view he had 
taken of the subject, and I was able, by having 
thinner and more perfect sections than he had, soon 
to determine the question of this nummuline layer,, 
which completed the proof which was already all 
but perfect in my estimation. Still there are certain 
gentlemen who, from time to time, renew the discus¬ 
sion upon the matter when I am not present to' 
reply to them, as was lately done at the Liverpool 
meeting of the British Association. Yet I venture 
to say that all the most eminent scientific autho¬ 
rities are fully satisfied with the view that was origi¬ 
nally put forward by Dr. Dawson, and supported by 
myself, also by Mr. Parker, Mr. Hymer Jones, Mr. 
Brady, and all those who have most carefully ex¬ 
amined it, and who are considered authorities on 
foraminiferous structure, and these views I have no- 
question whatever will ultimately prevail. I may 
say, also, that those gentlemen who are the best 
authorities on the microscop'c structure of minerals 
are entirely at one with us. Mr. Sorby, of Sheffield, 
who is by far the highest authority upon certain 
points of mineral structure, Mr. David Forbes, who 
is a great authority on the microscopic structure of 
minerals, and Mr. Maskelyne,—all say that this can¬ 
not be a mineral; that there is nothing that can 
account for the peculiar character that this structure 
shows that we know anything of in mineralogy, and 
there are certain facts which are quite inconsistent. 
I may just mention one of them, because I find it 
most satisfactory to any one who knows anything at 
all about the structure of minerals. It is this, that 
the Eozoon-rock shows, as many of them do, recent 
and fossil, distinct planes of crystalline cleavage. 
This has been long known. The spines of the 
Cidaris have a distinct crystalline axis; in fact, there 
is sometimes great difficulty in sawing them across, 
because the least turn of the saw will cause it to 
splinter off by crystalline cleavage. It has never 
happened to myself, but I am informed that many of 
the bags of gall-nuts which are sent over from the Le¬ 
vant very often contain a number of the curious large 
club-shaped fossil spines of the Cidaris, being put in 
fraudulently to add to the weight. Any of you who- 
