1890.] MICKOSCOPICAL J0UK:NAL. 43 



with a sliding piece to fit the one body, thus doing away with the dou- 

 ble and triple nose-pieces, which soon become unsatisfactory from their 

 tendency to wear and become loose at the collar-joints. 



Another very unique device was an iris diaphragm, to be used in 

 connection with the Abbe condenser, and which commends itself for 

 the simplicity of its manipulation. 



Two aplanatic lenses, one for use in the dissecting microscope, the 

 other for low-power hand purposes, made by the well-known Steinheil, 

 were also shown. Probably the most interesting of the Doctor's exhi- 

 bit was the new illuminating apparatus called the Koch or Wolz lamp. 

 It consists of a plain, round burner kerosene lamp, mounted on a 

 stand that can be raised and lowered. It is covered by a chimney or 

 japanned sheet iron with two tubulations on alevel with the most lu- 

 minous part of the flame, each tubulation holding a solid glass rod, 

 one straight for the top light and the other curved for illuminating be- 

 neath the stage of the microscope. The rods are made of a new 

 apochromatic glass, which has the peculiarity of transmitting a soft 

 yet intense white light without apparently giving off any lateral rays, 

 thus enabling the observer to w^ork in a dark room and dispense with 

 the aid of mirror or condenser. 



A very fine series of photo-micrographs was added to the society's 

 collection, one of the number a photograph of Pleurosigma aiigula- 

 tum^ being taken at an amplification of 4,000 diameters with perfect 

 definition. All the accessories noted, with the exception of the Stein- 

 heil lenses, were made by the celebrated optician, Carl Zeiss, of Jena, 

 Germany, and were greatly admired by the members present for the 

 fine workmanship. 



A description of the improved Pasteur filter, called the Chamberlin 

 filter, occupied a portion of the evening. It consists of a heavy metal 

 casing enclosing several unglazed porcelain tubes that are fitted to the 

 hollow cover of the outer casing ; the water is admitted to the lower 

 part of the large cylinder, and is forced through the porcelain tubes 

 into the hollow cover, which is secured to the cylinder by heavy screws 

 and a rubber packing. 



The filtering capacity of a 3-tube filter, about a foot high, is a gallon 

 of purified water in five minutes with the ordinary pressure of city 

 mains. 



Dec. 11^ i88g. — Reception. — Four large tables were each presided 

 over by one of the members, who followed the programme of exhibit- 

 ing and elucidating as many objects as could be shown during twenty, 

 minutes. Then each exhibitor transferred his microscope and accesso- 

 ries to the adjoining table for a like space of time, and so on, till each, 

 in turn, had occupied all the tables, thus giving visitors the benefit of 

 the entire range of subjects presented without having to change their 

 places. 



A. H. Breckenfeld handled two binocular instruments, showing a 

 series of objects with polarized light through one, and another set of 

 mounts by transmitted and reflected light with the other. Among the 

 polarizing subjects were brucine crystals, kinate of quinia, young 

 oysters (rolling in fluid), toe of wdiite mouse 2iXiA formica rufa (the 

 wood ant) ; by transmitted light, Rinnbock's geometrically arranged 



