I. MICROSCOPES. 767 



3556. New Portable Microscope. John Browning. 



This powerful and complete instrument, fitted with a sub-stage, accessory 

 apparatus, polariscope, &c., is contrived to fold on a hinged joint in such a 

 manner that when set up it is the size of an ordinary microscope, but when 

 closed, it packs in a case of which the outside measurement is 6 x 6 x 9. 



3557. Microscope Stand with Chain Movements, exhi- 

 bited in 1851. 



Educational microscope. Plain stage, with dividing English 

 object glass 2-inch, 1-inch, J-inch. In cabinet. 



The same with mechanical stage, with 1-inch 15, and J-inch 

 70., English objectives ; in cabinet. 



Dissecting microscope, 3 powers. 



Dissecting microscope, with glass stage and mirror, 3 powers. 



Pocket microscope, for collecting diatomaceae, &c. 



Pocket microscopes, for botany, entomology, &c. 



William Ladd $ Co. 



3557a. Polarizing Microscope, large Des Cloiseaux pattern, 

 capable of being placed either horizontally or vertically by means 

 of a joint and clamp, with all requisite accessories for the complete 

 study of the optical bi-refracting properties of natural or artificial 

 crystals, such as a goniometer for measuring the distance between 

 optical a'xes in air or in oil, at various temperatures ; ice-pan for 

 oil ; copper stove with thermometers and spirit lamps ; the micro- 

 scope frame and Nicol polarising prism, both being movable by 

 means of a rack and pinion. M. A. Picort, Pai^is. 



3557b. Polarizing Microscope, large pattern, with all 

 requisite accessories, the body of the microscope alone being 

 movable on the stand. M. A. Picort, Paris. 



3557c. Polarizing Microscope, small pattern, mounted 

 vertically with a small goniometer for measuring the distance 

 between axes in air. M. A. Picort, Paris. 



3558. Microscope (Small Model), with a Cylindrical 

 Clip for Objectives. 



Geneva Association for Constructing Scientific Instru- 

 ments. 



This model of a microscope is at once strong and simple. The system of 

 the cylindrical clip is as follows : 



The objective is not screwed upon the tube, but it is only pressed by a 

 spring against a carefully turned bearer. To take up the objective, it is 

 sumcient to draw it away transversely after having lowered it so as to exert a 

 pressure in the direction of the axis. The objective is more easily placed in 

 position than removed. The advantages resulting from this arrangement 

 are : 



1. A great saving of time to the observer, the magnifying changes by the 



objective being feasible instantaneously. 



2. The mechanical centering of the whole objective is better than that usually 



obtained with the screw. 



