We may summarise what precedes by saying that, up to about 1850, history continued to be, both for historians and the public, a branch of literature. An excellent proof of this lies in the fact that up till then historians were accustomed to publish new editions of their works, at intervals of several years, without making any change in them, and that the public tolerated the practice. Now every scientific work needs to be continually recast, revised, brought up to date. Scientific workers do not claim to give their works an immutable form, they do not expect to be read by posterity or to achieve personal immortality; it is enough for them if the results of their researches, corrected, it may be, and possibly transformed by subsequent researches, should be incorporated in the fund of knowledge which forms the scientific heritage of mankind. No one reads Newton or Lavoisier; it is enough for their glory that their labours should have contributed to the production of works by which their own have been superseded, and which will be, sooner or later, superseded in their turn. It is only works of art that enjoy perpetual youth. And the public is well aware of the fact; no one would ever think of studying natural history in Buffon, whatever his opinion might be of the merits of this stylist. But the same public is quite ready to study history in Augustin Thierry, in Macaulay, in Carlyle, in Michelet, and the books of the great writers who have treated historical subjects are reprinted, fifty years after the author's death, in their original form, though they are manifestly no longer on a level with current knowledge. It is clear that, for many, form counts before matter in history, and that an historical work is primarily, if not exclusively, a work of art.[219] II. It is within the last fifty years that the scientific forms of historical exposition have been evolved and settled, in accordance with the general principle that the aim of history is not to please, nor to give practical maxims of conduct, nor to arouse the emotions, but knowledge pure and simple. We begin by distinguishing between (1) monographs and (2) works of a general character.