HARD WICKE'S S CIENCE- G OS SI P. 



9 



all these at his command, except, perhaps, the glass 

 rings, which, on this side the Atlantic, are sold for 

 more than their weight in gold ; consequently, those 

 familiar with a "small dodge" buy not, but make. 

 And these " home-brewed " affairs are quite as useful, 

 if not so ornamental, as those cut with a diamond. 



"With whom originated the idea of making rings by 

 punching out the centre of a thin cover I do not 

 know. Beale refers to it in his " How to Work with 

 the Microscope," and my impression is that its mention 

 may be found in microscopical literature of a date 

 earlier than that of his book. However, for cells of 

 moderate depth they are superior to tin, zinc, or 

 vulcanite. 



In a brass plate \ inch or less in thickness, drill 



Fig. 5. — Growing-cell. 



lioles to correspond with the openings in the rings of 

 the various sizes desired, and with Canada balsam 

 cement thin covers over these holes ; place the plate 

 •on the kitchen stove for a few minutes, or until the 

 balsam will cool hard ; when entirely cold boldly 

 thrust an iron nail through the glass. If the cementing 

 has been properly done the fractures will not extend 

 beyond the edge of the hole in the plate. The two 

 secrets of success are to have the balsam reach quite 

 to the edge of the aperture in the brass, and to be 

 ■cold. If the balsam flows over toward the centre of 

 the cover the fractures made by the nail will extend 

 irregularly to the edge of the cement, and the ring 

 can then be completed by grinding the glass away to 

 the brass, giving the nail a rotation in addition to its 

 downward movement. Do not draw the nail upward. 

 A gentle heat will loosen the cover, and a slight 



rubbing with gasoline will clean it. Gasoline I have 

 found to be a kind of universal solvent for cements 

 microscopical, and wonderfully impressive. 



In the " American Monthly Microscopical Journal," 

 June 1882, Mr. C. H. Kain describes a similar plan, 

 using in his method sheet wax instead of Canada 

 balsam. With wax I have always failed, smashing 

 covers till on the verge of thin-glass bankruptcy. 



Having punched the covers, to make the growing 

 cell cement the small disc in the centre of a slip, take 

 a ring with a quarter inch aperture, break a little 

 piece from one side, and fasten this broken circular 

 band about the central circle, as in fig. 5. From 

 another ring with a | or larger aperture break a piece 

 as before, and cement about the inner ring, so that 

 its broken part shall be opposite the unbroken curve 

 of the former, and the cell is made. 



To use, place on the central disc a small drop of 

 the water containing the organisms to be kept alive, 

 and over it arrange a large square cover, taking pains 

 to prevent the water from overflowing into the inner 

 annular space. With a camel's hair pencil carefully, 

 and in small quantities, add fresh water at the top or 

 side of the square, until the space covered by the latter 

 and bounded by the outer ring is filled. It will be 

 found that this water will flow between the square 

 and upper surface of the exterior ring, will enter 

 through the break in the latter, partially filling the 

 outer annular space, and by capillary attraction will 

 occupy a part of the vacancy between the cover and 

 the interior ring, as shown by the diagonal lines in 

 the diagram, fig. 5, but unless too much water is 

 used, or is supplied in too great quantities at a time, 

 it will not pass the opening in the inner ring, thus 

 leaving an abundance of air to supply the animal life 

 under observation. The imprisoned air at once 

 becomes saturated with moisture, as evidenced by the 

 fogginess of the cover ; the central drop cannot 

 evaporate, and the external water will not come in 

 contact with it if care is taken in filling and in adding 

 that lost by evaporation. When not in use, the slide 

 is placed across a small vessel of water, a double and 

 twisted thread arranged in contact with the edge of 

 the square cover, and the whole left for another 

 examination at some future time. 



Dr. Alfred C. Stokes. 



Trenton, N'eiu Jersey, U.S.A. 



Cormorant in Worcestershire. — In October, 

 1882, a fine specimen of the above was shot on the 

 large reservoir between Cofton Hackett and Alve- 

 church. What I think to be a still more unusual 

 visitor to the Midlands is the Manx Shearwater, a 

 specimen of which was, in September, 1873, caught 

 in a hedge by some terriers when I was out walking 

 at Trygull, near Wolverhampton. Though much 

 exhausted, the bird seemed otherwise uninjured. — 

 K. D., Cofton Hackett. 



