188 PROCEEDINGS OF SOCIETIES. 



that two gentlemen, whom it was thought desirable to have as Presi- 

 dents, had been prevented from accepting the office. He trusted that 

 with this explanation they would receive his humble services during 

 the coming year. 



The minutes of the preceding meeting were read and confirmed. 



A list of donations to the Society was read, and the thanks of the 

 Society were voted to the donors. 



The Secretary announced that the special vote of thanks passed at 

 the last meeting had been sent to Mr. Hogg, and duly acknowledged 

 by him. 



The Secretary read the following letter which he had received that 

 day, in explanation of an error which had been printed in a former 

 number of the Journal, and which had been noticed in the number for 



March. 



2. Lansdowne Crescent, W., March 5, 1873. 

 My deae Mr. Slack,— I shall feel obliged if you will communicate to the 

 meeting to-night that I admit I have made an error at page 52 by inadvertence 

 and haste. The magnifying power should be one more than the distance of 

 distinct vision divided by the focal length, instead of one less; so that the 

 examples will read 8| times instead of 6| ; 81 instead of 79. I regret the error ; 

 but console myself with the sentiment that we are none of us infallible. 



I am, yours very truly, 



G. W. KOYSTON-PIGOTT. 



The Secretary exhibited to the meeting a pattern chimney for 

 microscope lamps which had been placed in his hands by Mr. 

 Wenham. It was a cylindrical brass tube with a space cut out of one 

 side of it, this being closed by an ordinary plain glass slide held in 

 its place by means of a spring clip. The chimney itself was in- 

 destructible, and if the slip of glass got broken by accident, it could, 

 of course, be very easily replaced. He also wished to mention that 

 at the last meeting some slides were sent to the Society from Mr. Allen, 

 of Felstead ; they contained some crystals obtained from a liquid dis- 

 tilled from coke, as described in the last number of the Journal, at 

 page 125. There was not time then to say much about them, but 

 having had his attention directed to it, and having in his greenhouse 

 a slow-combustion coke stove, he had obtained and examined some of 

 a similar liquid. He found that when the coke was wet or impure a 

 great deal of matter came over, it appeared to be a mixture of tar with 

 a corrosive fluid. On a damp day it formed freely, and it was so 

 corrosive that it perfectly riddled a piece of ordinary tinned iron 

 piping placed to receive it. He had sent some which was unusually 

 free from tar to Mr. Bell, who had kindly examined it. 



Mr. Bell said that he found the crystals deposited on evaporation 

 to be proto-sulphate of iron. The liquid contained sulphuric acid ; 

 there was also with them a little hydrochloric acid. Probably in the 

 first instance the sulphur was given off from the coke as sulphurous 

 acid, and this, by contact with the air and moisture, would become free 

 sulphuric acid, the action of which upon the iron would of course be 

 very rapid. 



Mr. Richards reminded the meeting that he had some time ago 



