In appearance the "Diatoms" resemble the chemical crystals. These "Diatoms" are minute one-celled living "Things," having a hard but thin siliceous covering or shell, of extreme delicacy. They are what are known as "microscopic" creatures--that is, visible only through the microscope. Some of them are so small that it would take a thousand or more to cover the head of a pin. But, remember this--the microscope reveals them as "living creatures" performing vital functions. They are found in the deep waters of the ocean. To the naked eye they appear like fine sand or "dirt," but under the most powerful microscope, they are seen to comprise many species and varieties, exhibiting many peculiar shapes and forms--in fact, they have been called "living geometrical forms," their shapes and appearances almost exactly resembling those of the chemical and mineral crystals. Science informs us that these and similar microscopic creatures, number thousands of families or species,--and it is thought that the varieties of microscopic creatures outnumber the varieties of creatures visible to the unaided sight. And, remember, that there is probably a still greater world of "sub-microscopic" creatures, that is a world invisible even when the most powerful microscope is used. Who knows what wonders are to be found there--what forms of creatures live, and move and have their being there. In passing by the subject of the resemblance between the outward forms of living things and the crystals, it is interesting to note how the crystals of frost and ice resemble the forms of leaves, branches, flowers, foliage, etc.--the pane of glass covered with these frosty forms, resembles a garden. The disk of saltpeter, under the effect of polarized light, very closely resembles the form of the orchid.