242 
SCIENCE. 
they could not fail to come in contact before vitality is 
lost. A half hour after contact with the milt, the eggs 
swell and become too hard to be broken by pressure of 
the thumb and finger. Their specific gravity is now so 
nearly equal to that of salt water that when the water is 
at rest they float upon its surface, remain suspended in 
the water, or occasionally sink slowly to the bottom. 
The least current will cause them to be distributed 
through the liquid. Mr. Earll discovered a small oil 
globule in each egg which serves the purpose of buoying 
it. The impregnated egg is also so transparent that the 
fishermen, who are not usually very observing, would 
never suspect their presence. The eggs are smaller than 
eggs of almost any other species, and have an average 
diameter of only one-twenty-eighth of an inch. It has 
been estimated, it will be seen, that 21,952 would make 
a cubic inch, and a quart of 57^ cubic inches would 
hold 1,267,728 eggs. 
The period of hatching is greatly influenced by the 
temperature of the water. The average temperature dur- 
ing the experiments at Crisfield was 84 Fahrenheit. Ten 
hours after contact with the milt the outline of the fish 
could be discerned by the naked eye. The fish is formed 
with the curve of the back at the lowest point of the egg. 
In fifteen and one-half hours the fish began hatching. 
In eighteen hours one-half of the eggs had hatched, and 
in twenty hours all were out. Experiments in water at 
78° Fahrenheit showed that twenty-four hours were nec- 
essary for hatching. A more remarkable effect of tem- 
perature is obseivable in the case of the cod. In water 
at 45 0 cod have been hatched in thirteen days, but in 
water at 31° fifty days were occupied in hatching. 
The newly-hatched macke.iel are about one-eighth of 
an inch in length, and so small as to escape through wire 
cloth with thirty-two threads to the inch, and are almost 
colorless. The food sac, situated well forward, is quite 
large in proportion to the body, the anterior margin ex- 
tending to the lower jaw. While floating on its back for 
several hours, during its helpless condition, it passes 
safely over the heads of its enemies, and is protected from 
being wrecked in sand or weeds. After a few hours, be- 
coming more vigorous, it gels to a depth of an inch or 
more below the sui face of the water. After a day or two 
the food sac is less prominent, and the fish experiences 
less difficulty in swimming at various depths. The young 
mackerel hatched by Mr. Earll were so hardy that forty 
were confined in a goblet without change of water for 
two days before the first fish died; o.hers placed in water 
which was allowed to cool gradually and immediately 
transferred to water ten degrees warmer, were not in- 
jured in the least. In fresh water they slowly sank and 
died in a few hours. Mr. Earll also found that a fair per- 
centage ot eggs could be hatched in still water with but 
one or two changes during their development. Eggs 
taken at 6 P.M., and allowed to remain in a basin of water 
till morning, when another change was made, hatched 
with very small percentage of loss. Samples ot all the 
different stages of development were preserved in alcohol 
and glycerine for the National Museum. Over half a 
million were hatched by the various methods and at vari- 
ous times. 
The apparatus used in these experiments consisted 
simply of floating boxes with bottoms made of wire 
cloth. The cloth was plated with nickel to prevent in- 
jurious ac ion of the salt water, and contained thirty-two 
wires to the inch. After it was found that a lot of fish 
had escaped through it, only the shells remaining to 
prove that hatching had actually taken place, the wire 
and each aperture were covered with coarse cotton cloth. 
The boxes were provided with covers for protection 
against storms, or wind, or rain, but were provided with 
openings on the sides to admit fresh water from above. 
The commissioner has been intensely gratified at these 
results due to the ingenuity of Mr. Earll. They open the 
way to the systematic propagation of the species in waters 
where they do not now exist, and to the countless multi- 
plication of them in the Chesapeake. The season being 
in mid-summer will not conflict with the shad season 
of the Spring, the salmon season of the Fall, or the cod 
season of the Winter. The eggs are much more abund- 
ant and hatch more easily and rapidly than those of any 
fish now propagated. During the tour days consumed 
in hatching a lot of shad, five lots of mackerel could be 
hatched, and during the twenty-four days necessary to 
hatch one lot of cod-fish, -thirty-two lots of mackerel 
would be produced. A suitable station for hatching was 
chosen at Cherrystone, Md. The fishermen are kindly 
disposed and will render every assistance. It is hoped that 
young fish may be thus successfully planted as far North 
as Narragansett Bay. 
Smithsonian Institution, Washington, ) 
D.C., November 6, 1880. \ 
THE ISLAND OF MONTREAL.* 
By William Boyd. 
A considerable portion of the waters of the Ottawa, at the 
foot of the Lake of Two Mountains, divides on the Island of 
Montreal. The branch that is directed to the northern part 
of the island soon sub-divides on Isle Perrot. There 
rapids are in each of the sub-branches. The sub-branches 
encounter the St. Lawrence on its northern side at 
two points, — shortly after it leaves the Cascades Rapids 
and below Isle Perrot, from that island’s inner shore. 
The waters of the St. Law-rence bound also, indirectly, 
the southern side of the Island of Montreal, flowing 
in the same river-bed with the Ottawa, but beyond 
or outside its stream. The water of the St. Lawrence 
is greenish, that of the Ottawa reddish-brown. The 
two rivers run side by side unmixed to the Ottawa’s 
lowermost mouth, at the foot of the Island of Montreal ; and 
thence onward in the same manner, with increased volume 
on the part of the Ottawa, to Lake St. Peter, where they 
finally mingle. If the Ottawa should cease to exist and the 
St. Lawrence remain, what is now the Island of Montreal 
would probably — from the high level of the then Lake of 
Two Mountains, and from a great fall which would, on the 
extinction of the Ottawa, take place in the St. Lawrence 
below the Cascades Rapids — be an island no longer ; but 
if the St. Lawrence should disappear and the Ottawa re- 
main, the Island of Montreal would continue to be an island 
still. Therefore the writer is of the opinion that the Island 
of Montreal is an island not in the St. Lawrence as has 
heretofore been held, but in the Ottawa. 
FRIEDRICH MOHR’S LIFE AND WORKS. 
By Dr. Geo. W. Rachel. 
On September 28, 1879, Prof. Friedrich Mohr, one 
of the greatest philosophers Germany has ever produced, 
died after a short illness at Bonn on the Rhine. He was 
born at Koblenz on November 4, 1806, and, therefore, at 
the time of his death, was nearly 73 years old. In spite of 
this advanced age, he remained active and bright almost to 
the very moment of death, dictating to his daughter Anna 
until within a few hours of it in his usual clear and coher- 
ent manner. 
His father was a pharmacist and proprietor of one of the 
principal drug-stores of the town ; he is described as hav- 
ing been unusually proficient in the arts of his trade, and an 
ardent lover of his special profession as well as of science in 
general. A wealthy man, comparatively speaking, he be- 
stowed great care on little Friedrich, the only surviving 
child ol six. The opportunity offered to the sickly, quiet 
boy who had to be kept from school during the greater 
part of his boyhood, was eagerly taken advantage of by him. 
Test-tubes and retorts almost took the place of play-toys 
with him, and his involuntary leisure enabled him to lay the 
foundation for his future greatness, viz. : an ability for lab- 
ratory work almost unsurpassed. Thus it was that his 
methods as well as many of the instruments and apparatus 
he devised, are found to-day in every laboratory and are used 
all over the globe wherever chemistry has an abode. 
* Read before the A. A. A. S., Boston, 1880. 
