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speak of it in the highest terms of commendation. The wheel of diaphragm 
at the side has an obvious use — to regulate the supply of light. 
Powell and Lealand's Patent Illuminator for Minute Opaque Objects. 
Collins' Webster’s Condenser . — Some time back we called attention to this 
excellent instrument, which, however, was then in an embryonic condition. It 
has since become developed under the hands of the inventor and manufacturer, 
and is now, all things considered, the best, cheapest, and most useful piece of 
accessory apparatus connected with the microscope. It consists simply “ of 
a double concave lens, cemented to a very deep crossed lens,” fixed in a 
suitable body, and capable of being fitted beneath the stage of any ordinary 
microscope. Below it is provided with a wheel of diaphragms, so formed 
that oblique light may be obtained, or direct light, or by a stop the effects of 
dark ground illumination may be produced. In addition, it has one of 
Mr. Collins’ new graduating diaphragms. For all the powers from the 
inch to the T Vth inch this instrument supplies all that the microscopist 
requires ; and it has the advantage of not requiring to be changed. In its 
present form it is achromatic, and is manufactured by Mr. Collins, of Great 
Titchfield-street, Oxford-street. 
Collins’ Webster’s Condenser. Graduating Diaphraghm of Condenser. 
A New Groicing Slide . — The examination of living objects under the 
microscope is a subject of great interest, though attended with considerable 
difficulty. It is by no means easy to prepare without injury a specimen of a 
growing plant for microscopical investigation. A new “ growing slide,” as it is 
termed, therefore promises to be of much service. This contrivance is the 
invention of Mr. H. L. Smith, an American naturalist, and presents the 
following features. It is composed of two glass plates 3X2 inches, and 
