10 
in her. Her sailing qualities do’ not at all 
unfit her for our work. Her cabin has ample 
accommodations for four persons, and could 
stow eight; and the cuddy forward has room 
and all the utensils for the cook: so that cruises 
to a distant dredging-ground can be undertaken 
without inconvenience, by a fair-sized party. 
Of the usefulness of the Chesapeake zodlogi- 
cal laboratory we may feel assured, though it 
is still in its infancy. It has held six sessions. 
During that time there has been a total attend- 
ance of fifty, of whom fourteen have been in 
attendance at least two sessions. ‘These fifty 
men have been gathered from more than twelve 
different colleges, and are at present located 
in fourteen different states, besides two who 
came from Canada, one from Cambridge, Eng., 
and one from Japan. 
In 1879 the laboratory was in co-operation 
with the Maryland fish-commission ; and Dr. 
Brooks devoted most of his own time during 
the season to a study of the oyster, with espe- 
cial reference to its embryology and its artifi- 
cial propagation. ‘The theoretical results of 
his work are of the greatest significance ; but 
he succeeded in artificially fertilizing the oys- 
ter’s eggs, and shedding such light upon the 
habits of reproduction that the greatest interest 
was aroused, and zeal in the search for some 
practicable method of oyster-culture, to replen- 
ish the waning oyster-beds. This interest has 
resulted in the discovery of a practicable 
method. 
I will not recapitulate all the scientific papers 
published as resulting from work done in the 
laboratory: suffice it to say, that important 
memoirs have been published upon Lingula, 
Squilla, Leucifer, Renilla (the last two being 
published in the Philosophical transactions of 
the Royal society), Thallasema, and a mono- 
graph, not yet complete, of the Hydromedusae 
of the south coast. Beside these memoirs, the 
various members of the laboratory have writ- 
ten numerous shorter papers, which have been 
published in the Quarterly journal of micro- 
scopical science, the university Studies, and 
Carus’s Zoologischer anzeiger. These articles, 
-embodying the results of the laboratory’s work, 
number, in all, fifty-nine separate titles. 
For the most part, the laboratory has been 
morphological in the aspect of its work; not 
exclusively so, however, for both in 1881 and 
1883 Dr. Sewall worked there upon selachians 
with reference to the equilibrium-sense func- 
tion of the semicircular canals. 
Last summer (1883), after three years i 
Beaufort, the laboratory was moved back to 
the Chesapeake Bay, and located in a building 
SCIENCE. 
[Vou. IIL, No 
rented from the Hampton normal school. The — 
location was in many respects not a good one, 
for it was far away from the best collecting- 
grounds and supplies of pure salt water; but 
it was selected to permit the laboratory to 
co-operate with the Maryland state oyster com- 
mission in experiments upon artificial propa- 
gation, and other expedients for a rapid and 
reliable method of restocking the oyster-beds 
in Chesapeake Bay. Lieut. Winslow, U.S.N., 
detailed for special service, was with us during 
most of the summer; and in the early part of 
the season the oyster-police boat, Gov. Hamil- 
ton, was stationed at the lower end of the bay. 
The results of the season’s work are not yet. 
so far worked up as to permit one to speak 
about them. We had among us Mr. William 
Bateson of Cambridge, Eng., who came over 
to work upon Balanoglossus. His work in- 
cludes a more thorough knowledge of the lar-. 
val history of Balanoglossus than has been 
hitherto attained, and promises much that will 
be of greatest interest in respect to that most. 
problematical creature. Hrnry L. Osporn. 
THE DETERMINATION OF THE OHM. 
Tue importance of having a uniform stand- 
ard of electrical resistance is so apparent, 
that the establishment of a unit which shall be 
suitable for practical work, and will also satisfy 
the demands of electrical science, has for a 
number of years been regarded by all electri- 
cians as of the first importance. 
The requirements of such a standard are, that. 
it shall be easily reproduced or verified ; that it 
shall have a simple relation to the units of work, 
heat, etc., and therefore be based on the funda- 
mental units of length and time; and, finally, 
that it shall be of so great resistance as to be 
suitable for all ordinary practical work. ° 
In the year 1862 the British association de- 
cided that a unit of resistance based simply on. 
the earth quadrant, or ten million metres, as. 
the unit of length, and the second as the unit. 
of time, would be of such a magnitude as to. 
best satisfy the requirements of the case. Ex- 
periments were then undertaken by a commit- 
tee of the British association with a view to. 
the construction of standards which should 
accurately represent this unit of resistance, or 
ohm as it was called. Owing to some minor 
defects in experimentation, and to an unac- 
countable error in the determination of the co- 
efficient of self-induction of the revolving coil, 
their result was in error. This standard Brit- 
ish association unit, as it is now called, is con- 
fessedly too small; but it is the basis of the 
