152 THE AMERICAN MONTHLY [July, 



lamp-rest which slides on cleats attached to the corner braces, and has 

 an upright for concave reflector when desired. //, sliding carrier for 

 camera, with tongued arms of sufficient width to bring the photographic 

 lens collar pi'ecisely over the microscopic tube when centered on either 

 base. /, set screw to retain it in position, andy, milled head of pin- 

 ion by which it is racked down to attach camera, K^ to eye-piece of 

 microscope. This light-tight connection is made with one-half of 

 child's rubber ball, perforated in centre to fit neck of eye-piece, and of 

 sufiicient size to fill the collar of the photographic lens. 



Fig. 2 illustrates the use of the stand in copying, enlai'ging, and re- 

 ducing, and requires but little explanation. TV, iV, base board, 5x1 

 inches, 4 feet long, grooved on edges to receive tongues on arms of 

 camera carrier. It is hinged to apex of wedge-shape block, O, the gud- 

 geon of which fits snugly into the hole in centre of supplemental base. 

 6\ telescopic boxes, i?, /?, slat passing beneath the camera carrier, with 

 upright, ^, for cai'rying the picture to be copied, the distance respec- 

 tively between the lens and picture and lens and ground-glass being 

 regulated by the operator without leaving his position at the focusing 

 scixen, so that all copies may be brought to a uniform size, as for lan- 

 tern slides, without regard to the size of the original. Removing the 

 telescopic boxes and slat, we have a convenient camera stand for in- 

 side use, the lateral movements being secured by the gudgeon attach- 

 ment, and the vertical by the screw brace, P. 



If used ordinarily as a microscope stand, the instruments are always 

 in line and position for photo-micrography. 



Distribution of Diatoms. — Mr. Isaac Robinson, of Hertford, 

 England, says : 



" The distribution of the diatomacese is much assisted by the swollen 

 condition of our streams and rivers after heavy rains, and in many cases 

 they contribute an appreciable proportion of the muddy coloring matter 

 which the river contains. On the Sth of April I took from the river 

 Lea at Hertford, for the purpose of microscopical examination, one pint 

 of water. The water was at the time much discolored in consequence 

 of there having been a considerable rainfall on the previous day, amount- 

 ing to nearly half an inch. On carefully examining the solid matter 

 contained in this small quantity of water, I was surprised to find upwards 

 of fifty species of diatomaceae, some of which were very numerously- 

 represented. I should state that these were not such as were simply 

 floating on the river, but that, after agitating the surface of the water, 

 the bottle was filled by placing its neck several inches below the surface. 

 This distribution is further facilitated by dry dust in summer, and what 

 is known as dust storms, in the solid matter of which Ehrenberg de- 

 tected upwards of a hundred species." 



o 



Staining Sections. — Very fine cellular structures may be rendered 

 plainly visible by coloring them with an ammoniacal solution of car- 

 mine, to which a surplus of acetic acid has been added, and afterwards 

 allowing them to remain for two to ten hours in a weak solution of 

 ferric sulphate. This is a very useful method for bringing nuclei into 

 view. The black coloration appears to be quite durable. — Verhandl. 

 d. Ces. Detitsch. Naturf. u. Aertze. 



