From the PREFACE of Volume II.
This second volume of The Tannins is devoted to the results of investigation by the author on the astringent principles from nine species of oaks and one species each of mangrove, canaigre, and chestnut.
In accordance with the announcement made in Volume I., there has been associated with these results so much descriptive matter, from the author's observations and other sources, as has been necessary to complete a foundation for the intelligent study of the subject.
The sources of these tannins have received careful attention, and every precaution taken to insure the genuineness of the samples from which the tannin was extracted.
The various oak barks were collected by the author himself or his assistant, with the exception of two samples, one from Dehra Dtin, India, the other from Herefordshire, England. The two last-mentioned specimens were obtained in anticipation of a possible criticism, that only the tannins from the oaks of Northeastern United States were investigated. Having em- ployed material from three different quarters of the globe, it is reasonable to assume that the conclusions regaining the oak tannins are not based on too narrow foundations.
Since the issue of the first volume the gathering of the bibliography has been steadily carried on. Many sources, not then accessible, have been consulted, so that now, in the two volumes, this index contains a total of nearly one thousand titles.
The illustrations are from pen drawings by my friend Edwin Thorpe, who possesses that rare combination of artistic and botanical knowledge which eminently fits him for the work ; to him are due my sincere thanks for the special consideration which he gave to this subject for the present volume.
Much credit is due to my assistant J. C. Peacock for his untiring energy and devotion to the chemical investigations. The constant attention necessary to conduct these could not have been given by the author alone, and it is not too much to say that without his assistant's help this volume could not have been written when it was.
My thanks are also due to Professor H. R. Procter, of Leeds, England, for the sample of Herefordshire oak bark and for contributions to the bibliography, and to David Hooper and A. E. Wild, both located in India, for samples of oak bark from the Himalayas.
It may not be out of place here to make it known that the author is very desirous of samples of bark from Quercus infectoria, in Asia Minor; also that he would like specimens of bark from the most important oaks of our Pacific slope. In all cases the botanical origin should be known absolutely beyond a doubt.
