The object of these biographies is to demonstrate the fact, unknown apparently to many critics of the Church, that there are numerous stars of science (and many more than this series includes) who were also devout Catholics, and found no difficulty in maintaining both positions simultaneously. It ought to be superfluous to maintain such a thesis, and it would be so if persons who propagate such accusations as are made against the Catholic Church would, first of all, investigate the facts of the case. But, as the statement has been made, it may be well to give some definite examples of the coexistence in the same individual of scientific enthusiasm and reputation with a steadfast attachment to the doctrines of the Catholic Church.<br><br>As only a selection is possible, it has been thought desirable that such selection should embrace a collection of subjects as varied as possible. Hence the persons whose lives are here sketched are taken from different countries, from different ages, and from different branches of science - biological and physical.