100 
NOTES AND MEMORANDA. 
the shells of organisms which live at the surface and not at the bottom, 
and that this deposit, which is of the same nature as the ancient chalk, 
differing in some minor respects, but essentially the same, is absolutely 
formed by a rain of skeletons. These creatures all live within 100 
fathoms of the surface, and being subject to the fate of all living 
things, they sooner or later die, and when they die their skeletons are 
rained down in one continual shower, falling through a mile or couple 
of miles of sea-water. How long they take about it imagination fails 
one in supposing, but at last they get to the bottom, and there, piled 
up, they form a great stratum of a substance which, if upheaved, 
would be exactly like chalk. Here we have a possible mode of con- 
struction of the rocks which compose the earth, of which we had pre- 
viously no conception. But this is by no means the most wonderful 
thing. When they got to depths of 3000 and 4000 fathoms, and to 
4400 fathoms, or about five miles, which was the greatest depth at 
which the ' Challenger' fished anything from the bottom— and I 
think a very creditable depth too — they found that, while the surface 
of the water might be full of these calcareous organisms, the bottom 
was not. There they found that red clay so pathetically alluded to 
by my friend on the right [Commander Stewart, who replied for the 
Navy] as the material to which when glory called him he might be 
reduced. This red clay is a great puzzle — a great mystery — how it 
comes there, what it arises from, whether it is, as the director has 
suggested, the ash of Foraminiferae ; whether it is decomposed pumice- 
stone vomited out by volcanoes, and scattered over the surface ; or 
whether, lastly, it has something to do with that meteoric dust which 
is being continually rained upon us from the spaces of the universe — 
which of these causes may be at the bottom of the phenomenon it is 
very hard to say ; it is one of those points on which we shall have 
information by-and-by." 
Comparative Photographs of Blood. — The ' American Naturalist ' 
for May states that Dr. J. G. Eichardson, for the sake of illustrating 
in criminal cases the distinguishable appearances of different kinds of 
blood, has flowed drops of blood from different animals so nearly in 
contact on the glass slide that portions of the two drops appear in the 
same field, and can be photographed together. Dr. C. Leo Mees has 
modified this method, and obtained exquisite results in specimens pre- 
sented to the microscopical section of the Tyndall Association. He 
spreads the blood by Dr. Christopher Johnston's method, which is to 
touch a drop of blood to the accurately ground edge of a slide, and 
then draw it gently across the face of another slide, leaving a beauti- 
fully spread film. In this way one kind of blood is spread upon the 
slide and another on the cover. When dry, one-half of each is care- 
fully scraped off with a smoothly sharpened knife, and the cover in* 
verted upon the slide in such position as to bring the remaining 
portions of the film into apposition. Under the microscope and in 
the photograph the two kinds of blood appear in remarkably fine 
contrast, even those bloods that are too nearly alike for safe discrimi- 
nation in criminal cases being easily distinguished when thus prepared 
from fresh material. 
