March 'jth, 1922.] Proceedings. xix. 



reservoir, into which the water fell and passed from there down 

 the pipe leading to the bottom of the tube containing the 

 pebbles, to be used again. In this apparatus he washed 1,000 

 cubic feet of air in 11 J da3'^s. 



This apparatus was made at first in glass, but he found the 

 alkali in the glass prevented him from determining whether the 

 air contained free mineral acid, so he re-constructed the 

 apparatus in celluloid. The most remarkable results were that 

 in using glass he obtained no free mineral acid but considerable 

 quantities of combined chlorides and sulphates. When using 

 celluloid he obtained free sulphuric acid and sulphates, but no 

 trace of hydrochloric acid or chlorides. He left water in contact 

 with celluloid for some weeks, and found no free acid had been 

 dissolved from it ; but on treating celluloid powder with boiling 

 water he obtained both free sulphuric and nitric acid ; so for 

 further experiments the celluloid must be discarded and the 

 apparatus constructed on a larger scale with silica tubes and 

 provided with more powerful pumps. The pumps he used drew 

 about 10 cubic feet of air per hour. 



The machine used by Mr. Thomson for smoke estimation in 

 the air was exhibited; also the apparatus for washing large 

 volumes of air with small quantities of water, and both were 

 shown at work. 



Ordinary Meeting, March 7th, 1922. 

 Mr. T. A. Coward, M.Sc, F.Z.S., F.E.S. {President), in the 



Chair. 

 A vote of thanks w^as passed to the donors of the books upon 

 the table. 



Dr. W. M. Tattersall read a paper entitled : — 



" The sound-producing mechanisms of Crustacea." 



The Manchester Museum has recently received two very 

 interesting collections of Crustacea, one from the shallow waters 

 and shores of East Africa and the other from Australia. There 

 are one or two species new to science and several interesting 

 records from the point of view of geographical distribution. 

 Full details will appear in the final report. A number of the 

 species collected exhibit mechanisms for the production of 

 sound. Three main types of sound-producing mechanism are 

 met with in Crustacea, (i) Popping Type. The sound is pro- 

 duced by the rapid withdrawal of a round peg from a socket 

 into which it fits very tightly. The mechanism may be likened 

 to the withdrawal of a cork from a bottle and the noise produced 

 is very similar to that made by the pop of a cork. (2) Fiddle 



