little over ten inches, in thickness seven inches, and in cir- 
cumference about three feet. It presented every appearance 
of having lain in the earth for a very considerable length of 
time ; but as it only reached Manchester on the day previous, 
the geological character of the gravel in which it was found 
had not been ascertained. 
Dr. Roberts drew attention to the injurious effects pro- 
duced by burning Pharaoh’s serpents in close rooms, and gave 
the particulars of a case which had lately come under his 
notice. 
Dr. Roscoe stated that in his opinion persons could not be 
too careful respecting the inhaling of even small quantities of 
mercury vapour, and he alluded in support of this opinion to 
the fact that two German gentlemen who were engaged in a 
London laboratory, in the preparation, for a scientific purpose, 
of volatile organic mercury compounds, had recently been 
poisoned by the accidental absorption through the lungs or 
skin of very small quantities of the vapours of these sub- 
stances. The symptoms characteristic of this form of mercu- 
rial poisoning are of the most painful and distressing kind, 
the first patient dying in a state of mania shortly after his 
admission into the hospital, and the second, on whom the 
effect became first perceptible three months after he had 
ceased to work with the substance, now lying in a hopeless 
state of idiocy. 
A paper was read “ On the Amount of Carbonic Acid con- 
tained in the Air above the Irish Sea,” by Mr. T. E. Thorpe, 
Assistant in the Private Laboratory, Owens College, com- 
municated by Professor H. E. Roscoe, F.R.S. 
The determination of the amount of carbonic acid contained 
in the atmosphere over the land has been made the subject 
of investigation by many experimenters, and from the results 
' obtained by Theodore de Saussure, Brunner, Boussingault, 
Angus Smith, and others, we are acquainted with the exact 
