analysed his impressions badly, or confused different events. Above all, we must ask when he wrote down what he saw or heard. This is the most important point: the only exact observation is the one which is recorded immediately it is made; such is the constant procedure in the established sciences; an impression committed to writing later on is only a recollection, liable to be confused in the memory with other recollections. Memoirs written several years after the facts, often at the very end of the author's career, have introduced innumerable errors into history. It must be made a rule to treat memoirs with special distrust as second-hand documents, in spite of their appearance of being contemporary testimony.
(3) The author states facts which he could have observed, but to which he did not take the trouble to attend. From idleness or negligence he reported details which he has merely inferred, or even imagined at random, and which turn out to be false. This is a common source of error, though it does not readily occur to one, and is to be suspected wherever the author was obliged to procure information in which he took little interest, in order to fill up a blank form. Of this kind are answers to questions put by an authority (it is enough to observe how most official inquiries are conducted in our own day), and detailed accounts of ceremonies or public functions. There is too strong a temptation to write the account from the programme, or in agreement with the usual order of the proceedings. How many accounts of meetings of all kinds have been published by reporters who were not present at them! Similar efforts of imagination