It would be no less a "practical" benefit if we were able in future to avoid some of the mistakes of recent years. Amongst these may be mentioned the views held up to the present day, that the resolution of lined objects depends upon the shadow cast in consequence of the obliquity of the light. Mr. Stephenson has reminded me of the derision (in which I joined) with which the object-glass of Mr. Tolles, with its marked aperture of 180°, was received; and yet at that time the demonstration existed that the effective angular aperture of an object-glass may readily exceed 180°.

Another instance may be found in that vexed question of a few years since, the Aplanatic searcher. At the time it did not seem to me unreasonable in theory that the defects of an object-glass might within limits be neutralized in the way proposed. The practical reason for not accepting the invention was the absence of results in the hands of anyone but its inventor; but no one was able to expound the principles, then well known elsewhere, which showed that its theory was unsound. If we had been aware of those principles we should have been able to discuss the claims of the invention in an intelligent manner and without having to depend solely on the want of results.

What seems to me to make the subject the more tempting is, that it is virgin soil; any of us who will take it up will not find it has been occupied before him, and the Society in receiving the results will not be in close competition as they are now with other Societies, in fact, we should then be working in a field of our own, the want of which has been so often bewailed among us.

The examination of diatom valves and Podura scales has undoubtedly been the cause of many improvements in object-glasses, and the indiscriminate abuse sometimes showered upon the observers is to a great extent undeserved: at the same time it is certain that there has been much misdirection of time and energy in such examinations, so far as the end proposed has been only to see with one glass for the hundredth time as nearly as possible what has been seen a hundred times before by a hundred other observers. Such examinations, if properly directed, would have advanced the knowledge of microscopical phenomena in general many years.

Of the two great methods of scientific inquiry, observation and experiment (or as they have been otherwise termed, "passive and active observation "), we have, I think, confined ourselves too much

again (p. 207), dealing with the effect of a particular kind of illumination on mineral structures, he says that it "would be equally applicable in the case of rods and minute fibres, and such kinds of structures as are commonly met with in organic bodies." And (p. 209), "Such general conclusions are more simple and obvious in the case of mineral structures, but are by no means confined to them. . . . and I cannot but think that much remains to be learned even in the case of more purely organic structures."

to the first, to the disregard of the second. So long ago as the time of Fontana, he wrote, "It is easy to view the image which is offered to the eye, but not so easy to form a judgment of the things that are seen, as an extensive knowledge of the subject, great patience, and many experiments will be found necessary for this purpose, for there are many circumstances where the images seen may be very similar, though originating from substances totally different, and it is here the penetration of the observer will be exercised to discover the difference and avoid the error."

To quote Sir John Herschel once more: "It has been found invariably that in those departments of physics where the phenomena are beyond our control, or into which experimental inquiry from other causes has not been carried, the progress of knowledge has been slow, uncertain, and irregular; while in such as admit of experiment, and in which mankind have agreed to its adoption, it has been rapid, sure and steady."

In microscopy experiment is, of course, more difficult of application than it is in some other branches of science, but there is still ample room for it; many instances will readily occur to you, such as those of the late Mr. Richard Beck on the Lepisma scales, Mr. Slack's silica films, and others, which have now and then appeared in our 'Proceedings.'

It may be that the work I suggest has already been in great part done; if so, it has not been recorded, and for all useful purposes might as well not have been done. It may also be that it is not so inexhaustible as I suppose; in that case there is the less reason for not exhausting it. Whilst I do not hold the view which some people in this country are fond of pretending to hold, that nothing valuable is to be found at home, and that everything abroad is necessarily of superior merit, we may at least set before us, as a goal worthy of being reached, the attainment of a position in our own particular branch of science on a level (to say the least) with that of other countries.

I know that those amongst you who hold my views are comparatively few in number. I have, however, put them forward now so that what it is we advocate may be understood, and others may possibly thereby be converted to the true faith. However erroneous or fanatical those views may be considered, I cannot think that any harm can result from thus stating them.

To the retort, "Physician, heal thyself," I can only say that it is a matter of no small regret to me, that with every inclination to lead the way, an insuperable barrier should be presented by the exigencies of my particular avocation, which not only reduce to small proportions my leisure hours, but render it necessary that those hours should be mainly employed in a recuperative process; * 'Discourse on the Study of Natural Philosophy.'

one evidence, however, that I can give of my sincerity is, to undertake a matter which I believe the Society would be doing good service to microscopy if it undertook itself, but which it can hardly be expected to undertake if it does not believe in its necessity, and that is to enable English microscopists to read in their own language one of the best modern German treatises-one which (as a deceased colleague on the Council of this Society declared) is a mine whose treasures might occupy many workers in developing."

Whilst it does not pretend to be exhaustive, it will at least serve (to put it no higher) to show how extensive a field a complete knowledge of the subject embraces, and until we are able to improve upon it, it will, I think, worthily supply the want which just twenty years since was referred to in an article in the Quarterly Journal of Microscopical Science':*-"The period has not yet arrived when all those who employ the microscope methodically as a means of scientific investigation possess an intelligent comprehension of the principles on which it is constructed and the nature of its powers as an optical instrument. There is a large region beyond mere manipulation into which few apparently care to enter. The writers of our introductory treatises leave the matter pretty much as they found it. Surely the time has arrived which calls for more than this; when an optical treatise on the microscope, worthy of the name, is not only desired by the few but required for the many."

When completed, the Society will be better able to judge whether I have exaggerated in what I have written. I have a strong conviction that the conclusion will be that I have not, and I have a strong hope that in the result a new departure will be made in "microscopy" in England.

*On the Optical Powers of the Microscope," by P. G. Rylands, vol. vii.

p. 27.