ARCHEOLOGY. 277 



Rome during the past years, has made a special study of this aspect of the 

 subject, with much success. 



Such correlations should prove to be particularly useful in the future 

 excavations at Rome, as at the Imperial Fora, north of the Forum Romanum, 

 and the principles and general hues of investigation may well be applicable 

 also at the future excavations at Chichen Itza under Dr. Morley. 



The other purpose is technical and applies chiefly to the mortar. The 

 Roman mortars offer excellent opportunity to study certain problems in the 

 characters and changes of the material that may be of useful application 

 to the study of modern cements. They are of special interest and importance 

 for the study of the changes brought about by the very slow chemical reac- 

 tions between the constituents, such as lime, sand, powdered brick, and 

 pozzolana, and, consequently, the characters that make for durability. The 

 Roman mortars have undergone a time-test of nearly 2,000 years under 

 conditions of actual use, a most severe test to which it is not possible, for 

 our study, to subject our modern materials. Some of them are still hard and 

 coherent, whereas others, made about the same time and existing under about 

 the same conditions, have become soft and friable. Study of the chemical, 

 mineral, textural, and microscopical differences between such mortars should 

 cast light on some of the factors that favor the production of a good mortar 

 or modern cement, and so should be of interest and value to the cement 

 industry. The ancient bricks and tuffs promise fewer results of purely tech- 

 nical interest, but a study of the Roman tuffs will be of interest for petrology 

 and volcanology. 



It is my purpose to make many chemical analyses of the specimens of all 

 three classes of materials and study thin sections of them under the micro- 

 scope; to study them, in fact, in much the same way that igneous rocks are 

 studied. The objects of the investigation present certain difficulties, because 

 of the vague and somewhat indeterminate characters of many of their mineral 

 components, their generally fine grain, and the indefiniteness of their textures. 

 The mortars also present certain special problems connected with their inves- 

 tigation for technical purposes, such as the character of the free or "soluble" 

 silica and the states of combination of the lime. These will demand the 

 working out, trial, and application of special chemical methods. 



It is suggested that specimens of the mortars from the ancient Roman 

 ruins near the modern Pozzuoli (the ancient Baiae) be collected, because 

 these will permit the study of the influence of the incorporation of the 

 peculiar pozzolana of this region, which was most favored by Vitruvius and 

 was considered to make the strongest mortar and to be particularly useful 

 for the making of hydraulic cement. An examination of the brick and 

 mortar of Pompeii might well be carried on in connection with ttie study of 

 the Roman materials. At Pompeii there is a definite end point (79 A. D.), 

 with the earthquake at 63 A. D. as another date, and the researches of 

 Mau and others have enabled us to distinguish between the pre-Plinian 

 building periods. The fact that much of the pozzolana used at Pompeii 

 came from Baiae adds interest to the Pompeiian materials. 



