To the microscopist who merely uses his microscope for the pleasure he can derive from it, rather than for serious study, it may appear that the plant life of the sea falls short of the animal life as far as interest is concerned. He may disabuse himself at once of this idea. There is no class of plants more interesting than the seaweeds and in few branches of plant life is there greater scope for new discoveries. The garden of the sea is largely an unexplored territory and there is no coast-line in the world of equal extent which provides so many different sea dwelling plants as our own. CHAPTER XVII THE MICRO-TELESCOPE AND SUPER MICROSCOPE Those of our readers who have borne with us thus far may quite excusably have thought that the last word had been attained in the construction of the microscope. It is true that different makers have made various improvements to their instruments, from time to time in recent years, most of them of minor importance but useful in the aggregate. But a few years ago, however, the advent of the Micro-Telescope and Super-Microscope marked an epoch in the manufacture of the microscope. We have shown that great strides were made in scientific investigation when the first simple lenses were manufactured, that there was a lull in microscopic research till the appearance of the compound microscope and now, when the latest instruments are in the hands of scientific workers, further possibilities are opened up. In all microscopes--the best as well as the cheaper instruments--there is one failing which very early forces itself upon the user. They have very little “depth of focus.” Let us explain exactly what the phrase means. Once or twice in our pages, we have recommended that the fine adjustment should be rotated to and fro while certain objects are being examined. When potato starch grains, for instance, are magnified sufficiently highly to show their characteristic markings, the whole of the grain cannot be seen clearly at one time, because at that magnification the “depth of focus” is slight. The higher the magnification the less is the “depth of focus”; when this quality is absent altogether only one plane of an object can be viewed clearly without re-adjusting the focus. With low magnifications, we may, to a limited extent, have more than one plane of an object in focus.