120 [Proc. B. N. F. C, 



— when a paper was read by Mr. Wm. A. Firth, " On Diatoms, 

 what they are, where and how they are found." Mr. Firth, 

 having devoted his spare time for many years to the study of 

 this microscopic group, and being acknowledged one of the best 

 mounters in Britain of these excessively minute organisms, 

 naturally drew an audience, including all the members of the 

 club interested in microscopic work. The popular manner in 

 which the subject was brought forward greatly enhanced its 

 value. The following is a summary : — 



The reader commenced by stating that the study of diatoms 

 has long been a favourite with the microscope, and intimately 

 connected with its progress. The first diatom was discovered 

 in 1773 by Professor Muller, a distinguished German, but little 

 progress was made in the study until the earlier part of the 

 present century. Since then great attention has been devoted 

 to the subject, and at the present time between 5,000 and 6,000 

 species have been discovered on the surface of the globe. Dia- 

 toms were described as tiny aquatic plants, so minute as to be 

 almost invisible to the naked eye, and found in fresh, brackish, 

 and salt waters. They are classed amongst the lowest vegetable 

 organisms, but differ from allied forms principally in the 

 possession of a silicious shell indestructible by the ordinary 

 agents of decomposition and heat. Descriptions of living diatoms 

 were given, and their remarkable motions referred to. The 

 construction of the silicious shells was also described, and it was 

 stated that of some species forty-one millions are required to 

 make one cubic inch, and that lines have been counted on their 

 surface over 100,000 in an English inch. Their distribution 

 was described as almost boundless where light and moisture are 

 favourably combined. The brown substance found on the stems, 

 and leaves of aquatic plants, also at the bottom of ditches and 

 pools in the milder seasons, consists almost entirely of diatoms, 

 and wherever found is characteristic of their presence. Large 

 deposits of their remains are found forming a portion of the 

 earth's crust, and are widely distributed. Several exist in our 

 own province, the most extensive being at Toomebridge, on the 



