32 KEPORT — 1864. 



the prepared organic liquid with tliis apparatus: by inserting it in quantities of 

 only a few drachms at a time into the hydrogen bottle, through the tubulated 

 funnel, and by employing sufficient spirit, no frothing could occur to endanger the 

 success of the experiment ; but it might at any moment be checked by the addition 

 of a little spirit down the funnel. If the tubes showed no deposit, and the paper 

 remained white, neither arsenic, antimony, nor sulphur could be present. The 

 black precipitate in the silver bottle would inferentially have been phosphide of 

 silver, but it admitted of absolute proof by testing with Scherer's process. The 

 operation being completed, the silver salt was passed through a filter previously 

 washed with acetic or nitric acid, and aftei-wards with ammonia, and the collected 

 black precipitate submitted to proof by burning the filter-paper. Acting on the 

 ashes with nitric acid and heat until oxidized, the silver precipitated by pure 

 hydrochloric acid, and the solution filtered, it contained all the phosphorus as 

 phosphoric acid, which could be tested by the nitrate of magnesia or the chloride 

 with ammonia, the characteristic crystals of triple phosphate of ammonia and mag- 

 nesia examined in the microscope and identified by the action of polarized light, 

 and the measurement of their angles in the goniometer, or by a solution of nitrate 

 of silver added -ttath ammonia, when the yellow phosphate of silver would be 

 obtained, and the blue phosphate of iron, with a solution of its protosalt. 



Memorandum on Ozone. By Dr. G. Kemp. 



On the Production of Cold by the Expansion of Air. By A. C. Kiek. 



On the Premature Decay of the Frescoes in the Houses of Parliament, its Cause 

 and Remedy. By "William Poole King. 

 The decay of frescoes first shows itself as a bloom, rendering the whole sm-face 

 dull and clouded ; soon after raised blotches appear, which become white and after- 

 wards drop ofl' in a dry powder, carrying off the colom- in patches from the fresco. 

 If walls built with mortar made from limestone of marine origin be examined in 

 cold weather, the pointing of the wall will be foimd to be covered with a bloom 

 which in places is lengthened out into needle-formed crystals, varying from -f^th 

 of an inch to 2 inches long. These crystals in warm weather change into a white 

 powder, and di-op otf, carrying much of the pointing of the wall with them. These 

 crystals, when examined chemically, are found to consist, for the most part, of sul- 

 phate of soda, sometimes, though rarely, mixed with nitrate of potash and nitrate 

 of lime, with small quantities of mm-iate of lime and magnesia. The droppings 

 from frescoes are composed of nearly the same materials, and are brought down by 

 the efilorescence of the sidphate of soda. To preserve frescoes, the sulphate of soda 

 in the wall should be kept in a dormant state by being always dry and warm. 



On an Apparatus for the Preservation or Disengagement of Sulphuretted 

 Hydrogen, Carbonic Acid, or other Gases. By Maxwell Lyte. 



On the Pollution of Rivers by the Sewage of Towns. 



By Dr. Stevenson MAc.iDAM, F.R.S.E., F.C.S. 



The author recently undertook a lengthened series of experimental observations 



on the pollution of rivers by the sewage of towns, with special reference to the 



contamination of the Water of Leith by the sewage of Edinburgh and Leith. The 



principal points brought out in the com-se of the investigation were — 



I. The chemical nature and condition of the Water of Leith as it arrives at 

 Edinburgh, and before being contaminated bv the sewage from the dwellings of 

 100,000 of the inhabitants of Edinburgh and Leith. 



II. The chemical composition of the liquids conveyed by the main sewers of 

 Edinburgh and Leith into the Water of Leith, by day and by night, during five 

 weeks in spring and ten days in summer. 



III. The analyses of the sedimentary matters found, in the open sewers draining 

 into the Water of Leith. 



I 



