796 
by Jules Marcou (p. 122), published at Zurich in 
1858. When it is remembered how the publication 
of American geological maps has increased in the 
past twenty-five years, the importance of this cata- 
logue will be appreciated. 
Bulletin No. 8, ‘On enlargements of mineral frag- 
ments in certain rocks,’ by Roland Duer Irving, is 
also in press. It will be illustrated with one wood- 
cut plate, five chromolithograph plates, and four 
woodcuts. 
SCIENCE- 
[Von. IIL, No. 73. 
eg 
Bulletin No. 7 begins the second volume. A num- 
ber of other bulletins are in course of preparation, 
and will soon be sent to the printer. Monograph 
No. vii., ‘Silver-lead deposits of Eureka, Nev.,’ by 
Joseph Story Curtis, is all in type with the exception 
of the index. It has a hundred and ninety-three 
pages, and will be illustrated with sixteen plates and 
ten figures. —— Monograph No. viii., ‘Paleontology 
of the Eureka district,’ by Charles Doolittle Walcott, 
is also in press, and is being rapidly put into type. 
RECENT PROCEEDINGS OF SCIENTIFIC SOCIETIES. 
Society of arts, Massachusetts institute of technology. 
May 22.— A paper by Mr. J. M. Batchelder was 
read by the secretary on the electro-deposition of 
iridium on engraved copper plates. A process had 
been used by Mr. Batchelder over twenty years ago; 
but it did not seem to have become known, and was 
presented as comparatively new. The solution was 
prepared by fusing iridium and osmium with three 
times their weight of nitrate of potassium for about 
one hour at a bright-red heat. A fused mass was 
broken into small pieces, and treated with nitric acid, 
in a glass retort with a condenser. The osmium 
was separated out, and the iridium which remained 
was treated with chlorhydric acid, after removing the 
nitrate of potassium by crystallization. The solution 
contained about one-eighth of an ounce of iridium 
to a gallon of water, to which about one-quarter 
pound of sulphuric acid should be added. The plate 
is to be immersed, and connected with the battery, as 
usual, and, when removed, will be found coated with 
iridium, closely resembling the common steel plates. 
Such plates, coated with iridium, were very durable, 
and possessed many other advantages. <A plate was 
shown which had been exposed twenty-seven years 
without protection; and its surface was still brilliant 
anduninjured. It is more easily wiped than a copper 
plate, the surface being, in this particular, about the 
same as a steel plate. Mr. S. H. Woodbridge read 
a paper on the heating and ventilation of the new 
Institute building, and the special principles involved. 
The building had not been planned with special refer- 
ence to any accepted system of ventilation, and only 
the circumstance of hollow walls rendered the intro- 
duction of such a system possible. Some of the more 
prominent features of the heating and ventilation 
System adopted are: the reversal of the ordinary 
custom of subordinating ventilation to economy in 
heating; basing the quantity of air required on deter- 
mined requirements rather than on cubic capacity 
simply; the use of large areas of air-passages, and 
low velocities; making the outlet areas smaller than 
the inlet areas, and some peculiar features of the 
flues; heating by large air volumes at low tempera- 
tures instead of by small volumes at high tempera- 
tures; some modifications in the construction of the 
fan, increasing the efficiency; the method of control- 
ling the temperatures of the coils; the method of 
determining the rate of condensation, and the daily 
aggregate condensation as a means of critical study, 
and of determining the cost of the heating and ven- 
tilation; and placing the ventilation and the tem- 
perature of each room under control of the engineer. 
The building measures about 150 by 90 feet, is 75 feet 
high, and contains some forty rooms, from 3,000 to 
60,000 cubic feet in capacity. In determining the 
requisite air-supply, regard was had to the maximum 
number of occupants, and the character of their work. 
Ordinary lecture-rooms receive 1,500 cubic feet per 
hour for each person; physical laboratories, where 
some gas-flames are used, get 2,000; ordinary chemical 
laboratories, 3,000; the organic chemical laboratory, 
4,000; and libraries, 2,000. The total capacity of the 
rooms is about 741,000 cubic feet, and the mean total 
air-supply about 3,535,000 cubic feet per hour, corre- 
sponding, with a uniform distribution, to a change of 
the entire air every twelve minutes. In the chemical 
laboratories, however, the air is changed every six or 
seven minutes. There are 79 flues, three feet by one 
foot, with a total area of about 230 square feet; and 
nearly one-half of these had to be located in the out- 
side walls, notwithstanding the objections to such an 
arrangement. ‘The finish of the flues is rough brick. 
Each inlet flue connects with but a single room, and 
the inlet is at about the middle of the height. The 
outlets are at the top and bottom of the room; the 
former being used only in hot weather, while the lat- 
ter are always open. There are three valves or dam- 
pers on the outlet flue, — one at the top, a check-valve 
at the bottom to prevent a reversal of the draught, 
and one at the top outlet of theroom. The inlet flues 
also have three dampers. The flues terminate in a 
sub-basement four feet high, under the whole build- 
ing, with a concrete floor. The air enters through 
large windows, and, after passing through the main 
coil, passes through the fan into the fan room, open 
on three sides, to the sub-basement. The fan is 
twelve feet in diameter, with twelve floats, and has 
a free delivery over its entire circumference. The 
power it requires is very small. Calculation showed — 
that the cost of heating the new building would be 
much greater than that of heating the old, on ac- 
count of thinner walls, and other sources of loss, 
besides the greater quantity of air supplied. The 
