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EDITOR's INTRODUCTION.

should be disposed to hope that in the future the progress of science will be even more rapid.

In the first place, the number of students is far greater; in the second, our means of research—the microscope and telescope, the spectroscope, photography, and many other ingenious appliances—are being added to and rendered more effective year by year; and, above all, the circle of science is ever widening, so that the farther we advance the more numerous are the problems opening out before us.

No doubt there are other Scientific Series, but it is not believed that the present will exactly compete with any of them. The International Scientific Series and Nature Series are no doubt useful and excellent, and some of the volumes contained in them would well carry out the ideas of the Publishers, but, as a rule, they are somewhat more technical and go into minuter details.

The names of the Authors are a sufficient guarantee that the subjects will be treated in an interesting and thoroughly scientific manner.

High Elms, Farnborough:

November, 1891.