The microscope should be, like the rest, as portable as possible. For most geological purposes high powers are not required, consequently a small microscope is sufficient.
It is sometimes of service, when working in a district where microscopic rock-sections are required, to carry a small collection of microscopic slices of selected or typical rocks or minerals for purposes of comparison. A series of fifty or one hundred slices can be packed in a box a few inches square.—Outlines of Field-Geology.
| ON THE ANNIHILATION OF THE MIND. |
By JOHN TROWBRIDGE,
ASSISTANT PROFESSOR OF PHYSICS, HARVARD COLLEGE.
THERE are some subjects which are unapproachable by any of the present methods of scientific investigation, yet the human mind, especially that form of it which is utterly untrained in scientific methods of thought, loves to ponder over the profoundest mysteries, and calls upon Science with an almost imperative tone to solve moral doubts and fears. One of the greatest questions which one finds is perplexing the general reader of popular science, who is also an independent thinker on religious questions, is that of the survival, so to speak, of the human mind and all that betokens the mental and moral power of man after death. The alarming doctrine that the mind and soul are the result of a process of growth in the individual, like physical growth of bone and muscle, and that body and mind increase and decrease together, and are resolved into the elements again at the close of life, is not infrequently put forward by materialists. It is maintained, further, that the belief in immortality is largely a matter of education, notwithstanding the evidence which is brought forward to prove that even uncivilized nations have a belief in deities and a future life. To the materialist, the picture presented by the unwrapping of a Peruvian family burial-sack, with its young and old mummies, and its collection of pottery and bag of grain to help the disembodied spirits on their w r ay to a happier hunting-ground, is pathetic only because it seems a hopeless superstition. What kind of a soul, it is asked, has the Digger Indian who is hardly more intelligent than a wild animal? If he has a mind and soul, so has my dog. No; what we call the soul is a cultivated state or condition which perishes like a highly-disciplined adaptation of the muscles of the body which a gymnast possesses. It is a state of crystallization; it is a reaction or interaction of atoms consequent upon physical growth. When the body dies, the mind and its attributes perish. Such utter disbelief in the great doctrine of the resurrec-
