8o 
SCIENCE. 
by this Time Service, the signals of which reach Bangor, 
Lennoxville, in Canada, Albany, and New York, as well as 
different points in Massachusetts. The copper time-ball, 
held by a powerful electro-magnet at the top of the mast 
on the Equitable Life Assurance Building, Boston, is re- 
leased at noon by the clock at Cambridge. During 1879 
accidents caused a small error in its fall on two days only, 
and on three days it has been dropped at I2h. 5T. os. 
The great equatorial of fifteen inches’ aperture and the 
meridian circle whose telescope has an aperture of eight 
inches have been kept actively in use for the last three 
years. The former instrument has been devoted almost 
entirely to photometric work. The problem of astronomi- 
cal photometry, roughly stated, is to determine the bright- 
ness of all the heavenly bodies, so that all may be compared 
with a single standard. Previous to the beginning of this 
work at the Harvard Observatory, photometric measure- 
ments had been made almost entirely upon the planets and 
brighter stars, and there was no definite knowledge of the 
amount of light emitted by the satellites and fainter stars. 
At the outset of the work several hundred measurements 
were taken of the brightness of the outer and inner satel- 
lites of Mars, which measures have been taken accurately 
nowhere else. The satellites of Jupiter and Saturn, includ- 
ing Hyperion, the faintest of Saturn’s satellites, were simi- 
larly measured. In addition to measuring their brightness, 
a large number of determinations of the positions of the 
satellites were made. A comparison was also begun of the 
light of the sun and stars, with the idea of reducing all 
photometric measurements to a common standard— the light 
of the sun. This photometric work has been continued 
until the light of all the known satellites, except the two 
inner satellites of Uranus, has been measured. 
One of the most important series of equatorial observa- 
tions has been in connection with the eclipses of ]upiier’s 
satellites. These phenomena have proved exceedingly 
valuable as a means not only of determining the orbits of 
the satellites themselves, but of measuring the distance of 
the sun or the velocity of light, and of obtaining terrestrial 
longitudes. 
The observations of the mere appearance or disappear- 
ance of a satellite, however, can not be rendered sufficiently 
exact, and, to lessen the errors, photometric observations 
have been made of the satellites as they gradually enter or 
emerge from the shadow of Jupiter, using the planet itself 
or another sate lite as a standard. 
In order to furnish means for the comparison of the 
scales of stellar magnitude, employed by different astrono- 
mers in their estimate of the brightness of faint stars, a 
number of faint stars in the immediate neighborhood of the 
north pole were selected for photometric measurement, and 
a circular was distributed among astronomers requesting 
estimates of magnitudes of the same stars for comparison 
with such other, and with the results of the measurements 
made here. A series of measurements of all the planetary 
nebulae has also been undertaken. This work with the 
great equatorial has necessitated the invention of a number 
of new photometric instruments, which have been devised 
by Professor Pickering and his assistants. 
For nearly eight years Professor Rogers has been engaged 
upon one of the largest astronomical undertakings that has 
been successfully completed in this country. This is the 
observation with the meridian circle of the zone of eight 
thousand stars, between fifty and fifty-five degrees north, 
undertaken by this Observatory as its share in the determi- 
nation of the position of the stars of the northern hemis- 
phere. The observations were finished about a year ago, 
but some years will be required to complete the reduction 
and publication of this work. 
The total number of observations for 1879 with the meri- 
dian circle, including about six hundred for the Coast 
Survey, was nearly three thousand. The scientists at the 
Observatory are now engaged in the task of determining 
the light of all the stars visible to the naked eye in the lati- 
tude of Cambridge. The meridian is used in observations 
like a transit instrument in connection with a new and 
elaborately designed photometer. 
At the Museum of Comparative Zoology the staff of 
specialists is almost entirely occupied in the classification 
and arrangement of different collections and the publication 
of the results of their researches. The most important 
accessions during 1878 and 1879 are the extensive collec- 
tions of the Blake dredging expedition, and the collections 
of birds, mammals, reptiles, and fishes, made by Mr. Garman 
at St. Kitts, Dominica, Grenada, Trinidad, St. Thomas, and 
Porto Rico, after he left the Blake. The Blake collections 
and specimens from the entomological, conchological, and 
ornithological departments are in the hands of well-known 
specialists for final investigation. Of the extensive work 
in progress it is impossible to give any details. The results 
are embodied in the extensive publications of the museum. 
Five volumes of bulletins have been published, averaging 
about a dozen papers each. The quarto publications will 
hereafter be issued as memoirs. The catalogues thus far 
published have been collected into Volumes I.-IV. of the 
memoirs. Five volumes of memoirs and the first part of 
the sixth have already appeared. The second part of the 
sixth and Vol. VII. are now in course of preparation or in 
press Vol. VI. contains the great work upon which Pro- 
fessor Whitney is now engaged, “ The Auriferous Gravels 
of the Sierra Nevada of California.” The Sturgis Hooper 
Professorship of Geology, held by Professor Whitney, is 
noticeable as being founded solely for original research. 
The dredging operations of the Coast Survey steamer 
Blake have not only aided zoological science by the infor- 
mation obtained in regard to echini, corals, crinoids, ophi- 
itrians, worms, hydroids, and others, but have added to 
geographical knowledge of the Caribbean Sea by showing 
the changes in form and distribution of lands along various 
groups of islands, and in the form of the land beneath the 
water. Professor Agassiz considers the deep-sea collections 
of the Blake the largest and most important ever made on 
this coast, and, when combined with the results of other 
expeditions sent out under the auspices of the Coast Sur- 
vey, they make the collections at the museum but little 
inferior to those of the Challenger. During the coming 
summer Professor Agassiz will probably undertake another 
dredging trip in the Blake, following the course of the 
Gulf Stream to the north of the Bahamas, and dredging 
from the 100 to the 2,500 fathom line off the coast of the 
United States, so as to connect the isolated district with the 
deep-water fauna proper of the Atlantic. 
Professor N. S. Shaler, Professor of Paleontology, in ad- 
dition to his work at the museum, and as an instructor, 
has, since 1873, had charge of the Kentucky State Survey. 
Four volumes of reports and one of memoirs have been 
already completed, and one volume of memoirs and nine 
of reports are now in press. The recent writings of Pro- 
fessor Shaler are ‘‘The Origin and Nature of Intellectual 
Property,” and several articles in the “ Proceedings of the 
Boston Natural History Society,” “ The Atlantic Monthly,” 
and “The International Review.” The article by Pro- 
fessor Shaler in the latter magazine is entitled “ Sleep and 
Dreams.” 
Scientific publications, based entirely or in part upon 
the entomological collection of the museum, are the new 
edition of the “ Catalogue of the Diptera of the United 
States,” by Osten-Sacken, published by the Smithsonian 
Institution, Part VIII. of the “ Monographic Revision of 
the European Trichoptera,’’ by R. McLachlan, published in 
London, and several papers by Dr. H. A. Hagen, the head 
of the department. 
At the medical school the largest amount of original in 
vestigation is carried on in the physiological and chemical 
laboratories. In the former a number of new forms of ap- 
paratus are in use, which have been designed by Professor 
Bowditch and his assistants. Among these are an appar- 
atus for keeping animals alive by artificial respiration ; a 
dog-holder, canulae for observations on the vocal cords of 
animals, without interfering with their natural respiration ; 
unpolarizable electrodes used in studying certain problems 
in the physiology of the nervous system ; a new form of 
apparatus for barometric measurements ; and a novel plan 
for measuring the volume of air inspired and expelled in 
respiration. A new lorm of plethysmograph has been 
devised by Dr. Bowditch. This is an instrument for meas- 
ing the changes in the size of organs, either hollow or 
solid, which are produced by variations in the conditions 
to which they are subjected. The essential part of Dr. 
Bowditch’s invention is a contrivance by which fluid is 
allowed to flow freely to and from the organ to be measured 
without changing its absolute level in the receptacle into 
