340 WAITMAN CROSS 
less satisfactory. But no classification of this period could have 
been really adequate, because the chemical and mineralogical 
compositions, as well as the origin, of many rocks were unknown, 
and only modern methods of research have permitted the assign- 
ment of a large number of types to their proper relationships. 
Abbé R. J. Haiiy.— The first systematic arrangements of rocks 
to be of much importance to the science of petrography as now 
understood were evolved in Paris, and the controlling idea of 
these systems has dominated French petrography fora century, © 
and is evident in all systems to some extent. 
The Abbé R. J. Hatiy was professor of mineralogy at the 
Museum of Natural History in Paris and in charge of its great 
cabinet of minerals. As already mentioned, his conception of 
molecular structure and its relation to crystal form had placed 
mineralogy within its proper sphere. In 1801 he published the 
first edition of his classic work ‘‘Tvatté de minéralogie,” in four 
octavo volumes, with a fifth of quarto-size containing eighty- 
seven plates, filled for the most part with figures of crystals. 
This treatise is evidence at once of the advanced state of min- 
eralogy and of the non-existence of anything worthy of being 
termed a science of rocks, in France, at this time. The quarto- 
volume of the 7vaz#é contains a tabular view of Haiiy’s “ Distri- 
bution Méthodique des Minéraux.” To this elaborate system of 
minerals are added two short appendices presenting an arrange- 
ment of rocks. One is headed ‘‘Agrégats des différentes sub- 
stances minérales,”’ the other, ‘‘Produits des Volcans.” That 
the arrangement of rocks had not received much thought from 
Haiiy at this time is clear from the imperfect scheme presented 
and from the fact that it was not until 1811 that Hatiy addressed 
a letter to Leonhardt’s Taschenbuch fiir Mineralogie, saying that 
he had conceived the idea of classifying rocks mineralogically 
(‘‘J’ai congu l’idée de classer cette suite (des roches) minéral- 
ogiquement’’). 
Haiiy was nota geologist, and his system must be judged in 
the light of the circumstances under which it was constructed. 
These are trenchantly characterized by Lossen in his comment 
