NOTES AND CORRESPONDENCE. 
A Simple Trough for Zoophytes, &c.—Perhaps the following 
cheap and easy method of constructing a small zoophyte 
trough may be useful to some of your readers, as I have 
found such articles extremely convenient in the examination 
of small Sertularian and other zoophytes. 
Take an ordinary glass slide and cut it with a diamond 
into five pieces, A, B, C, D, E, as shown in fig. 1, or any 
iliger Ie ites OL 
glazier will do it for a trifle if the lines are first drawn with 
apen. The piece A being thrown aside, cement C, D, E, in 
their relative position on the middle of another slide, as 
shown in fig. 2, with marine glue. The piece B is to be 
cemented on the others, which it exactly covers, and the 
trough is complete. Being cut from one piece, C, D, and E, 
are certain to fit together. If more than one are being made, 
the covers, B, may be cut from thin slides, and thick ones 
may furnish the side pieces, C, D, E. Objects are, of course, 
introduced above, and are necessarily kept close to the front 
glass; this latter may be a square of thin glass for higher 
powers, as it can be easily replaced if broken. The contents 
are retained by capillary attraction, even when the body of 
the microscope is in an upright position; and the affair is as 
manageable on the stage as an ordinary object-slide.—GrorcE 
Guyon, Ventnor, Isle of Wight. 
Feb. 17th, 1863. 
The Photography of Magnified Objects by Polarized Light. 
—Crystals are generally looked upon as belonging almost ex- 
clusively to the polarizing class of microscopic objects. Their 
