president's address. 91 



allow the members to inspect the medals, to which he suitably 

 responded in the affirmative. 



Dr. Donkin then read his paper " On the Marine Diatomacece 

 of Northumberland," illustrating his remarks by most beautiful 

 specimens, exhibited under microscopes belonging to himself, Dr. 

 Embleton, Mr. H. B. Brady, and Mr. Marreco. He gave a brief 

 and interesting account of these beautiful creatures, which he 

 said were considered to be vegetable organisms, from their 

 resemblance to the Desmidice, a race of freshwater Algce, but the 

 rapidity of their motions, and other facts in their history, would 

 lead an observer to suppose that they were animals. He de- 

 scribed the curious siliceous shells, or shields possessed by them, 

 which from their indestructible character and their infinite 

 number, are found in some localities in immense quantities, espe- 

 cially in a fossil state, in which they form strata of considerable 

 thickness, known as fossil or infusorial earths, which, as Tripoli, 

 and under various names, are extensively used for polishing 

 metals. These siliceous shields, under the microscope, present a 

 most beautiful appearance, being delicately sculptured in designs 

 and patterns of infinite variety and beauty. They exist where- 

 ever water is found, and in the Antarctic Ocean are found in such 

 immense quantities that Dr. Hooker considered that, but for 

 them, the due quantity of oxygen in the air and water (without 

 which animal life could not exist) would not be maintained. 



Dr. Donkin gave an account of his own discoveries on the 

 Northumberland coast, which number some fifty species pre- 

 viously unknown to science ; he also described the mode of col- 

 lecting and preparing them. 



Mr. Daniel Oliver jun., F. L. S., then exhibited, under the 

 microscope, a large number of beautiful sections of wood prepared 

 by Mr. Thomas Atthey, of Cramlington, for the Museum at the 

 Royal Botanical Gardens at Kew ; and Mr. H. B. Brady, for 

 the information of the practical microscopists present, described 

 the method adopted by Mr. Atthey in preparing and mounting 

 these specimens. 



The Fourth and Last Evening Meeting of the session was 

 held on Thursday, the 17th of February, when about fifty gentle- 



