544 Mr. T. Andrews. [June 10, 



Results of Analysis expressed in parts per 100,000. 



Sewage No. 1 

 » » 2 

 Deep 'well-wa- 

 ter No. 1 



No. 2.. .. 

 Filtd. Thames 

 water 



Total 

 solid 

 matter. 



60-20 

 84-60 



43-44 

 42-34 



26-42 



Organic 

 carbon. 



2-350 

 7-550 



0-027 

 0-023 



111 



Organic 

 nitro- 

 gen. 



1-387 

 4-210 



010 

 0-007 



-021 



Ammo- 

 nia. 



Nitrogen 



as 

 nitrates 



and 

 nitrites. 



2- 200 



3- 500 





 





 



0-446 

 0-442 



0-202 



Chlorine. 



8-5 

 9 6 



2-5 

 2-5 



1-6 



In conclusion I have to express my indebtedness to my wife for the 

 great assistance which I have received from her in the most laborious 

 task of estimating the colonies on the gelatine plates, amounting to 

 nearly 1000 in number, which this investigation has entailed. 



XII. " Observations on Pure Ice and Snow." By Thomas 

 Andrews, F.R.S.E., F.C.S., Wortley Iron Works, near 

 Sheffield. Received June 10, 1886. 



The recent very severe winter afforded favourable opportunity and 

 material for investigating some of the properties of ice and snow. 

 The object of the following observations was to obtain information on 

 the relative conductivity of ice and snow, the dilatation of pure ice, 

 and its relative hardness or penetrability at various temperatures. 



Set I. — The Relative Conductivity of Pure Ice and Snow. 



The experiments on the conductivity of the ice were made as fol- 

 lows : — 47 gallons of distilled water at a temperature of 48° F. were 

 placed in a large circular iron tank, A, of the internal dimensions 

 given on fig. 1. Around this tank was built a brick enclosure, of 

 4 feet 2 inches internal diameter ; an opening was left near the bottom 

 for easily removing the expended freezing mixtures, &c. The inter- 

 mediate space between the iron tank and the brickwork was filled 

 with a freezing mixture of snow and salt, maintaining a constant 

 temperature of —4° F. throughout. 18 cwts. of this mixture 

 was required for each charge, and the charge was entirely renewed 

 every 12 hours during the 115j hours needed to freeze the above 

 volume of water. Thus about 8 tons of freezing mixture was used 



