376 



ness whenever the supply of air was not sufficiently rapid. On ex- 

 amining the air at the end of the experiment, no alteration had taken 

 place either in the total volume of air, or in the proportion of azote 

 which it contained ; the only perceptible change being the substitu- 

 tion of a certain quantity of carbonic acid for an equal volume of 

 oxygen gas, amounting to about half a cubic inch per minute, and 

 being equivalent to the addition of 96 grains of carbon in 24 hours. 



Two experiments were made on the respiration of oxygen gas, ob- 

 tained from chlorate of potash, and containing in the one case two, 

 and in the other only one per cent, of azote. Under these circum- 

 stances it was found that the volume of the gas was unaltered, and 

 that a similar quantity of oxygen gas had been abstracted, but that a 

 much smaller quantity of carbonic acid had been formed than in the 

 last experiment, the remaining portion being made up by azotic gas 

 which had been given out from the lungs of the bird, and the volume 

 of which was just equal to that of the oxygen absorbed. The bird 

 was somewhat distressed during the experiment, but recovered imme- 

 diately and perfectly on being released from its confinement. 



In the fourth experiment, in which a pigeon was made to respire a 

 mixture of oxygen and hydrogen, with a small proportion of azote, 

 (the oxygen being in the same proportion as in common air,) it was 

 found that there was no loss of oxygen ; but that a quantity of hy- 

 drogen disappeared, and was replaced by an equal volume of azote. 

 The authors observe that birds have a quicker circulation of blood 

 than other animals ; and also that they are more sensible to the sti- 

 mulating effects of oxygen. 



On the spontaneous Purification of Thames Water. By John Bostock, 

 M.D.F.R.S.SfC. Read April 30, 1829. [PM.TVaws. 1829, ;;. 287.] 



In the report which the author made of the result of his exami- 

 nation of Thames water to the Commissioners appointed by His Ma- 

 jesty to inquire into the supply of water in the metropolis, one of 

 the specimens, taken near the King's Scholars' pond-sewer, was de- 

 scribed as in a state of extreme impurity. The water had remained in 

 the laboratory unattended to ; but after an interval of some weeks it 

 was observed to have become clear, while nearly the whole of the former 

 sediment had risen to the surface, forming a stratum of half an inch 

 in thickness, and still emitting a very offensive odour. In process 

 of time this scum separated into large masses or flakes, with minute 

 air-bubbles attached to them. At the end of two months longer 

 these masses again subsided, leaving the fluid almost totally free 

 from any visible extraneous matter. On analysis the water was 

 found to contain lime, sulphuric and muriatic acids, and magnesia, 

 in much larger quantities than in the specimens of Thames water 

 previously examined, the proportion of saline matter being increased 

 four-fold. The proportion of the muriates is nearly twelve times 

 greater; that of carbonate of lime between two and three times, 

 and that of sulphate of lime five and a half times greater. The water 



