202 Scientific Proceedings, Royal Dublin Society. 



In the case before us only a general classification can be at- 

 tempted, and degraded forms could only be represented by a 

 special colour. 



This system presents us with certain advantages over the 

 ordinary graphic methods : for instance — on each glass plate is a 

 collection of the representatives of any group which occur in a 

 particular stratum. These forms are the chronological data of the 

 ordinary stratiographical geologist ; and it matters not to him how 

 these may be arranged upon the plane. 



The philosophical palaeontologist arranges the names on each 

 plane so as to indicate the relations of each animal to those preced- 

 ing and succeeding it in time, as well as to its synchronous neigh- 

 bours, and thus he gets a graphic view of the march of life ; by 

 looking from above down the vista of time he sees widely-separated 

 recent animals gradually converging till they all unite in some 

 form which, if at present unknown, must once have existed ; or, 

 more accurately, diverging from such a common ancestor. It will 

 also be made apparent that in every age there were forms which 

 varied from the parent stem, which lived for a longer or a shorter 

 period and then became extinct. 



"Very valuable museum demonstrations could be made by fitting 

 up a comparatively large apparatus, to the glass plates of which 

 were cemented real fossils with their names. Ammonites and 

 Brachiopods, for instance, are well fitted for this purpose. Afiini- 

 ties and variations would in this case be illustrated by the actual 

 specimens, and so be vividly impressed upon the mind. 



By drawing or etching on each glass plate a similar outline 

 map of the world on Mercator's projection, and by allocating one 

 of the smaller subdivisions of the Cainozoic period to each, the 

 migrations of animals could be indicated in terms of time and 

 space. This would naturally necessitate a separate series of 

 plates. 



It is needless to dwell further upon the possibilities of such an 

 apparatus ; for I feel confident that it will prove of use in many 

 other ways, and in other branches of knowledge than in those 

 indicated above. 



I may add that I have employed this system for nearly two 

 years, and have found it to answer admirably. 



