406 Notices of Scientific WorJcs. [July? 



or gas. The same kind of air is then shown to be evolved from 

 marble by the action of a red heat, quick-lime being left behind. 

 The properties of lime are then shown ; its evolution of heat when 

 slaked by water ; its non-effervescence on being treated with acids ; 

 its solubility in water ; its combination with the au' previously 

 evolved from it to reproduce marble. These phenomena are illus- 

 trated with ample experimental evidence, until the audience are 

 thoroughly familiar with the connection existing between quick- 

 hme, marble, and the gas evolved from it. The properties of this 

 gas are then explained ; the extinction of ordinary flames in it, and 

 its power to support the burning of other bodies are illustrated; 

 but it is not until a piece of carbon is actually obtained before the 

 audience by heating sodium in the gas which has just before been 

 evolved from a piece of marble, that the lecturer makes use of the 

 term carbonic gas, or leads any one to susj)ect that carbon in any 

 form is associated with marble. Having proceeded so for, the 

 lecturer shows how carbonic gas may be obtained in other ways ; and 

 the consideration of this subject naturally leads to the composition 

 and properties of air and the subject of oxygen and oxides, the ordi- 

 nary experiments with this gas being varied in a somewhat novel 

 manner. These subjects occupy the first four lectures. The fifth is 

 devoted to other forms of carbon, such as graphite and the diamond, 

 and liquid and solid carbonic gas ; whilst the concluding lecture 

 treats of carbonic di-sulphide, carbonous oxide, and the unburnuig of 

 carbonic gas by vegetation. From this part of the subject we are 

 tempted to make one or two quotations, which will serve to show 

 the clearness of expression with which Dr. Odling is so happily 

 gifted. " If you reflect a little, I think you will come to this 

 conclusion: that substances which grow — vegetable substances — • 

 are all of them destined ultimately to become burnt, or to undergo 

 a change equivalent to burning. A great deal of wood, for instance, 

 is c])opped up and used for fire-wood ; a great deal more is used for 

 building ships, for forming the interior portions of houses, and 

 making furniture. These ships and houses and furnitm-e last for a 

 certain time; they gradually pass from an honourable into a dis- 

 honourable condition ; old furniture is put into the lumber-room ; 

 the disabled ships are broken up and destroyed ; and at last they 

 go to the fire, where the carbon becomes oxidized or converted into 

 carbonic gas. But there is a great deal of vegetable matter which 

 never undergoes this burning. In the autumn a large quantity of 

 leaves fall to the earth, and there undergo some sort of change; 

 this change is in fact a very slow burning, but without the plieno- 

 mena of ignition which we see in the case of a fire, although the 



leaves are converted into carbonic gas or oxidized carlion 



But a great quantity of vegetable substance neither undergoes 

 burning nor decay, but is eaten. We know that cattle feed largely 



