Several scholars, both in Europe and America, have published the results of their studies relating to the problems of Inca history. Ernest Desjardins has written on the state of Peru before the Spanish conquest,[1283] J. G. Müller on the religious beliefs of the people,[1284] and Waitz on Peruvian anthropology.[1285] The writings of Dr. Brinton, of Philadelphia, also contain valuable reflections and useful information respecting the mythology and native literature of Peru.[1286] Mr. Bollaert had been interested in Peruvian researches during the greater part of his lifetime (b. 1807; d. 1876), and had visited several provinces of Peru, especially Tarapaca. He accumulated many notes. His work, at first sight, appears to be merely a confused mass of jottings, and certainly there is an absence of method and arrangement; but closer examination will lead to the discovery of many facts which are not to be met with elsewhere.[1287] A critical study of early authorities and a knowledge of the Quichua language are two essential qualifications for a writer on Inca civilization. But it is almost equally important that he should have access to intelligent and accurate descriptions of the remains of ancient edifices and public works throughout Peru. For this he is dependent on travellers, and it must be confessed that no descriptions at all meeting the requirements were in existence before the opening of the present century. Humboldt was the first traveller in South America who pursued his antiquarian researches on a scientific basis. His works are models for all future travellers. It is to Humboldt,[1288] and his predecessors the Ulloas,[1289] that we owe graphic descriptions of Inca ruins in the kingdom of Quito and in northern Peru as far as Caxamarca. French travellers have contributed three works of importance to the same department of research. M. Alcide D’Orbigny examined and described the ruins of Tiahuanacu with great care.[1290] M. François de Castelnau was the leader of a scientific expedition sent out by the French government, and his work contains descriptions of ruins illustrated by plates.[1291] The work of M. Wiener is more complete, and is intended to be exhaustive. He was also employed by the French government on an archæological and ethnographic mission to Peru, from 1875 to 1877, and he has performed his task with diligence and ability, while no cost seems to have been spared in the production of his work.[1292] The maps and illustrations are numerous and well executed, and M. Wiener visited nearly every part of Peru where archæological remains are to be met with. There is only one fault to be found with the praiseworthy and elaborate works of D’Orbigny and Wiener. The authors are too apt to adopt theories on insufficient grounds, and to confuse their otherwise admirable descriptions with imaginative speculations. An example of this kind has been pointed out by the Peruvian scholar Dr. Villar, with reference to M.