1 882.] Microscopy. 169 



America between the two seas. A canal via the lake of Nicaragua 

 was projected in 1548. Other explorations were made, for this 

 purpose, in the Isthmus of Tehauntepec and the Isthmus of 

 Panama. M. Alphonse Milne Edwards has recently been mak- 

 ing investigations in the waters of the Mediterranean. During 

 the seventy days ne was so engaged the greatest depth reached 

 by sounding and dredging was 2600 metres. The bottom was 

 found not devoid of living beings, species of low organization being 

 found between depths of 1068 and 2600 metres. At an average 

 depth of 250 metres the temperature was constant at 13 Cent. 

 This explains the small development of life in the depths of that 

 sea, the muddy bottom and the absence of rocks being also un- 

 favorable to germination. The report also confirms the belief that 



the Mediterranean is a sea of recent formation. The English 



missionary Mr. Pearson has recently returned home from Uganda 

 with a large amount of information concerning the country and 

 the Victoria Nyanza. He has surveyed the western shore of the 

 lake, taken many observations, and left a careful meteorological 

 journal. He speaks highly of the general accuracy of Mr. Stan- 

 ley's work and found that nearly all his latitudes were correct. 



■ The reinforcement of laborers for Mr. Stanley, numbering 



135. left Zanzibar for the Congo on October 20th. The Belgian 

 Association has abandoned its proposed expedition to Nyangvve 

 which was to have effected a junction with Mr. Stanley on the 



lower Congo. Petermann's Mittheilungen for November last 



contains a valuable paper by Ernest Marno on the Grass Barriers 

 of the Nile. 



MICROSCOPY. 1 

 A Hollow Glass Sphere as a Condenser for Microscopic 

 Illumination. — A glass globe filled with water has long been 

 employed by watchmakers and engravers for the purpose of con- 

 densing the light upon their work'; it was also used by some of 

 the early microscopists. Ledermiiller, in his " Mikroskopische 

 Gemiith-und-Augen-Ergozung " (Microscopic Mind-and-eye-de- 

 lights) 1763, gives a representation of his lamp and condenser; 

 the latter is a globe without foot or neck, and is supported on the 

 top of a square brass rod by six claws, the lamp being supported 

 in the same way, both of them sliding into square holes at the 

 opposite ends of a brass arm fixed on a stand. In the " Micro- 

 graphia," Hooke gives a figure of his microscope and accessories, 

 amongst them is a globe condensing the light on the stage of the 

 instrument. This form of condenser was probably used by many 

 of the old microscopists, but it appears soon to have fallen into 

 disuse, as it is not mentioned by Adams in his " Micrographia 

 Illustrata," 1771, or in his " Essays on the Microscope," 17S7. 

 Possibly the opticians of the period did not care to introduce so 



This department is edited by Dr. R. H. Ward, Troy, N. Y. 



