294 Analyse: of Books. [April, 



ing a little mercury, which was afterwards passed into the cylin- 

 drical part of the tube as a method of measuring it. By this 

 precaution, it was determined, for example, that the length 

 a a' of 10 millimetres ought only to be reckoned as two, &c; 

 the results which have been stated were obtained in this mode. 



When the apparatus was cold, a small bubble of gas was 

 observed to have been formed above the alcohol, but it pro- 

 duced a difference of only two millimetres in the level of the 

 mercury in the small tube above b' '. 



In order to determine the degree of heat at which the ether 

 and alcohol are reduced to vapour in these experiments, the 

 tubes containing these fluids were heated in oil, in which a 

 thermometer was placed. A cylindrical glass vessel was em- 

 ployed to contain the oil ; by these means it was easy to deter- 

 mine the moment at which the liquids in the tubes were reduced 

 to vapour ; it was found that ether required 160°, and the alcohol 

 207° of Reaumur. 



The apparatus above described for determining the pressure 

 exerted by ether and by alcohol, was also subjected to the heat of 

 the oil bath; but a refrigerator was previously adjusted to the 

 upper part of the small tube containing the column of air, by which 

 the temperature of the column was constantly kept at 18°. The 

 results, as to the degree of vaporization and to the pressure 

 exerted, agreed with those which have been described. 



When my memoir was read to the Academy, 1 announced that 

 water heated in glass tubes altered their transparency, so as to 

 prevent any observation of what took place ; since that period I 

 have found that by adding a small quantity of carbonate of soda 

 to the water, the transparency of the glass was much less 

 injured. By this method, I ascertained, although with some 

 difficulty, on account of the frequent breaking of the tubes, that 

 at about the temperature of melting zinc, water may be com- 

 pletely reduced to vapour in a space equal to nearly four times 

 that of its original volume. 



Article X. 



Analyses of Books. 



Transactions of the Royal Geological Society of Cornwall, 



Vol. II. 1822. 



We are happy to introduce to our readers' attention this 

 second volume of the labours of our scientific brethren in Corn- 

 wall ; the papers it contains are replete with facts that are of 

 much importance, not only in their applicability to practical pur- 



