I. MICROSCOPES. 917 



diameter. But it can only practically be done by a fine set of meclianic.il 

 motions in rectangular positions giving perfect command of the position of 

 the flame. 



3597. Apparatus for Continuous Observation of Minute 

 Organisms with the highest powers, by preventing evaporation of 

 the iiuid in which the organisms live. 



Rev. W. H. Dallingcr and J. J. Drysdalc, M.D. 



This apparatus was devised by Messrs. Dalliuger and Drysdale for prose- 

 cuting their " Researches into the Life-History of the Monads." It is used 

 upon the ordinary " mechanical stage " of the microscope, so as to admit of 

 the continuous examination under the highest powers of the same drop of a 

 putrefactive or' other fluid without allowing it to evaporate. The glass cup 

 to the right is to be filled with water. The capillarity of the linen carries 

 over a constant supply of moisture ; part of this linen is included in the 

 central cylinder into Avhich the object glass projects, and the water thus- 

 constantly carried into this air-tight chamber causes the air therein to become 

 so saturated that evaporation from the fluid under examination cannot take 

 place. The highest powers may be used, because the india-rubber diaphragm 

 yields instantl}- to the screw of the " fine adjustment." 



3598. Microscopic mounting materials and dissecting instru- 

 ments, consisting of: 



Wood-cutting instrument and chisel, instrument for catting 

 circles of thin glass, glazier's diamond, writing diamond, cell- 

 making instrument, brass table and lamp, Page's forceps, case of 

 dissecting instruments (containing four knives, two hooks, two 

 points, three pairs of scissors, three pairs of forceps, and needle- 

 holder), Valentin's knife, 1 oz. thin glass, 9 doz. slips (3 in. by 1 in.),. 

 3 doz. wooden slips. 3 doz. cells, 200 labels, 5 capped bottles (con- 

 taining Canada balsam, asphalte, gold-size, glycerine, and marine 

 glue), bottle of Deane's medium, three stoppered bottles for con- 

 taining chloroform, nitric acid, and liquor potassae. It. $ J. Beck. 



3603. Wew Sub-stage Condenser, comprising achromatic 

 condenser of high angle of aperture. James Sicift. 



The above is an effective spot lens, from 3 inch objective to ^ inch ; it has- 

 centering adjustments, contracting diaphragm, and complete polariscope, in 

 which all the colours of the rainbow can be obtained. It also forms a complete- 

 substitute for every piece of apparatus used under the microscope. 



3604. Low Angle Objectives. A series from 1 inch to 

 i inch. James Sicift 



3605* Popular Achromatic and Tinted Condenser. 



James Swift* 



This apparatus combines the achromatic condenser, light modifier, spot 

 lens, and polariscope. 



36O6. Microscopic Objects, illustrating every department 

 of microscopy. 



Machine for cutting sections, with knife. 



