It has been stated in another place that it is assumed the operator is not mounting diatoms simply as microscopic objects, but as instructive specimens. It is not, therefore, sufficient to take a single slide as all that is required, but to have the same diatom prepared in as many ways as possible. The following are the principal:-- 1. Mounted crude in fluid (see Chapter IV.). 2. Burnt crude upon the cover, and mounted dry or in balsam (as before mentioned). 3. Mounted dry or in balsam (see Chapter III.), after the cleansing process already described. I will here give Mr. Rylands’ method of mounting them _dry_, the fluid and balsam preparations being noticed in their respective chapters. The slide with the ring of asphalt, or black varnish, should have been prepared some weeks previously, in order to allow it to dry thoroughly. When required, it must be held over the spirit-lamp or Bunsen’s burner until the ring of varnish is softened. The burnt cover, having been heated at the same time, must then be taken in the forceps and pressed upon the softened varnish until it adheres all round. When cold, an outer ring of asphalt completes the slide. Such is the method which my friend Mr. T. G. Rylands employs in the preparation of diatoms for the microscope. I have said enough concerning his results. It is to be feared, however, that to some these several modes of operation may appear lengthy and complicated; but if read carefully, and the experiments tried, they will be found simple enough in practice, and to occupy much less time than an intelligible description would lead the novice to believe necessary.