1875.] Physics. 119g 
instrument towards the south from September to December, and gradually 
diminishing the inclination again till March, when it is replaced in a hori- 
zoutal position. One of the principal sides of the parallelogram represents 
the door, fixed on hinges, and giving access to all the interior. At the side 
opposite the door is fixed a clock, the dial of which is seen through a circular 
aperture in the side. To this clock is adapted a toothed wheel, moved by the 
drum containing the spring. This wheel only performs one revolution in 
twenty-four hours. To its axle is fixed by a movable screw a large drum of 
brass, the circumference of which is 520 m.m., and the breadth 16m.m. Upon 
the surface of this drum is fixed a slip of paper, as is done with the Morse 
telegraphs. A few seconds are sufficient for fixing or for removing this band. 
A slit in the box is so arranged that the sun’s rays, shining through it, fall 
upon the band, even when the luminary is very near the visible horizon. ‘The 
bands are prepared with chloride of silver by being steeped, first in a solution 
of common salt, and then, shortly before being used, in solution of nitrate of 
silver. 
The students in the Physical Laboratory of Owens College having occa- 
sionally experienced some difficulty in obtaining the spectra of some salts 
with the ordinary Bunsen, through apparently a deficiency of pressure in the 
gas, it occurred to Mr. F. Kingdon thatthe amount of light, even at this deficient 
temperature, might be increased by multiplying the number of luminous 
points. This is accomplished by broadening out the flame of the Bunsen; that 
is, causing the gas to issue through a narrow slit instead of a round hole. So 
far, only a rough experiment has been made, the slit being about Zin. long and 
lin. wide. ‘The result, as expected, wasa more brilliant spectrum. 
Mrcroscory.—In the Report of the Geological Survey of New Hampshire, 
some valuable information respecting the preparation of specimens of Diato- 
macez for examination and study by means of the microscope is contributed 
by Dr. A. M. Edwards, of Newark, New Jersey, U.S. Respecting the collection 
of Diatoms, some valuable hints are given. Arachnoidiscus, Triceratium 
Wilksii, and Aulacodiscus Oregonensis, may be looked upon for logs of wood 
which have been floating in the sea and imported from New Zealand or Van- 
couver’s Island. So on logs from Mexico and Honduras may be found the 
curious Terpsing musica. ‘the nets of fishermen from deep water may yield 
algz bearing such forms as Rhabdomena arcuatum or Adriaticum, Grammato- 
phora serpentina and marina, various Synedras, and other fine forms. On 
oyster shells may be found alge bearing upon their fronds Biddulphia regina, 
Bayleyti or aurita. After a ship is unloaded, and as it floats higher in the 
water, its sides may be searched for treasures of the Diatom world. The 
sea-grass, Zostera marina, often bears upon its waving ribbons fine forms of 
Diatoms, and that used for stuffing chairs and imported from abroad will 
yield foreign species to the collector. The apparatus and materials used are 
those found in the possession of most well equipped microscopists. The 
chemicals required are nitric acid, sulphuric acid, hydrochloric acid, bichro- 
mate of potash, caustic potash, alcohol, distilled water, and washing soda. 
Recent Gatherings.—Sand to be removed by shaking in clean water and 
pouring off before the diatoms, which are lighter than the sand, settle. After 
the diatoms have settled as much as possible of the water is to be poured off 
from the test-tube containing them. They are now covered with nitric acid 
andallowed to stand a few minutes. Usually some chemical action takes place, 
and 1t will be well to wait until it subsides, The tube or beaker is then held over 
the lamp and carefully heated until the reaction of the acid upon the organic 
matter of the diatoms ceases. Then, while the liquid is still hot, a few small 
fragments of bichromate of potash should be dropped in. The organic matter 
is more thoroughly destroyed in this way than when the acid is used alone. 
The acid and diatoms should then be poured into a capacious beaker of clean 
water, washing the test-tube out with a little water and adding this to the other. 
After the diatoms have settled, the supernatant fluid is carefully poured off, 
and a fresh supply added; this must be repeated until all the acid and coloured 
chromium compound has been removed. When this point is arrived at can 
only be ascertained from experience. 
