we agree with the poet Milton that "Peace hath her victories, no less renown'd than War," we shall have no difficulty in appreciating the statement that there are Heroes of Science. It goes without saying that the word Heroes does not signify Martyrs; fortunately, there have been very few martyrs of Science. Men need not sacrifice their lives because of their scientific beliefs. Wherever Men of Science have been imprisoned, and in a few isolated cases put to death, we shall find that it has been owing to their conflict with the religious beliefs of the people.

There have been martyrs of Science in other respects. Within recent years several X-ray operators, intent on healing disease in others, have been attacked by invisible radiations which have brought about a slow and lingering death. Then there have been cases of men willing that some dangerous experiment should be performed upon them, in the hope that others might benefit by the experience thus gained.

However, the Heroes whose lives we are about to consider are men who have been in the forefront of the advancement of knowledge. It is true that some of these have had to sacrifice much; to undergo great hardships and yet fight on. Some have had to suffer the ridicule of the wise men of their time, and the hatred of those who should have been their friends. But the word Heroes is used here in no such restricted sense, although it is certain that every Hero of Science must have made some sacrifice in his daily life. We may count all who have made a great advance in Science to be true Heroes. Of course, it is impossible to consider the lives of all such men.

Unfortunately, there are many of the Heroes of Antiquity whose biographies are almost entire blanks, while among the more modern Men of Science there are many who have done much useful work, but in whose lives there have been no outstanding features which would interest the general reader. For these reasons the Heroes selected for our present purpose are those in whose lives we find most of general interest; they are all prominent Men of Science.

Many of us, when children, received instruction in Biblical History, being told the story of some incident in the life of Joseph at one time, the story of Jacob at another, and the story of Moses at another time. Each story was of interest to us, but the interest was increased greatly when we found how all these individual stories were linked together. How old Jacob sent his sons to Egypt to buy corn; their meeting with Joseph; his settling his father Jacob, or Israel, in Egypt; the increasing descendants of Israel causing a later Pharaoh to fear for his kingdom; their consequent bondage; and the ultimate release of these children of Israel by Moses. For the same reason I have endeavoured to link up, so far as it is possible, the stories of the different Heroes of Science. I have gone back to the beginning of Science, some two thousand and five hundred years ago, and I have called a halt at the other end, only omitting the Scientists living at the present time.

This arrangement will help to emphasize the very long break in the advance of Science, which lasted throughout the Middle Ages. Indeed, we shall have to jump from the beginning of the Christian era right on to the time of Queen Elizabeth, with only two prominent stepping-stones between.