Notes and Correspondence

In case it should be thought worth notice, I beg to offer the following suggestion.

In Mr. James Smith’s paper “On a Dissecting Microscope,” in the last number of the ‘Journal ‘(Trans., page 13), it is remarked that different-sized objects would require the slips of glass at the bottom of dissecting troughs to be of different widths, and therefore necessitate the employment of several troughs, or else a glass trough furnished with several false bottoms of gutta-percha, fitted with various-sized slips of glass. I would venture to suggest that one gutta-percha trough might suffice, if the aperture and glass fitted into it were made wedge-shaped instead of paralied-sided, thus presenting various widths at different points. An opening, an inch and a half long, diminishing from half an inch in width at one end to nothing at the other, would accommodate various-sized dissections, and admit, if required, of their being operated upon the same time.—G. GUYON, Richmond, Surrey.

I inclose sketch of a Triarthra, of which I found several in a duck-pond at Chipstead, in Surrey, last August. As nothing like it is described in the ‘Micrographic Dictionary,’ nor in the last edition of Pritchard, it may be new.

The other sketch represents-a group of Vaginicolœ (?), of which several were found in a glass trough; but they contradict the assertion that Vaginicolœ are solitary or merely double. The gelatinous case in which these were lodged was very irregular, and with no trace of separate cells.—HENRY J. SLACK, 34, Camden Square.

An Astronomer’s Protest.—When Mrs. Malaprop said that “comparisons were odorous,” she only gave ungrammatical enunciation to a truth which must be admitted by everybody; and the recognition of which might have spared us from Mr. Henry U. Janson’s peroration in his “Farther Notices on Finders,” in your last number. Had that gentleman ever read Arago’s ‘Popular Astronomy,’ he would have learned that the determination of the exact tint of a star may lead to the resolution of very remarkable physical questions; while the study of the works of the two Herschels would have shown him that upon the sudden or gradual condensation of a nebula may hinge the interpretation of cosmical phenomena so stupendous that the most brilliant discoveries of the microscope pale in insignificance before them. I yield neither to Mr. Janson nor to any one else in my appreciation of the instruction and amusement to be derived from the microscope, but must protest against such a comparison as he makes, even though he may shield himself behind a parade of Dr. Goring’s ignorance of astronomy.—A FELLOW OF THE ROYAL ASTRONOMICAL AND MEMBER OF THE MICROSCOPICAL SOCIETIES.

Having, in my desire to keep up with the progress of improvement, procured a microscope constructed on the principle of Mr. Wenham’s last invention (Transactions, p. 15), I feel it my duty to declare that I have fully verified every statement made in the paper alluded to with regard to “the new combined binocular and single microscope.” I should call it an under-statement. In short, all I said of the former one (Memoranda, p. 66) will apply to the latter with redoubled force. That was excellent, but this is 5wper-excellent!

The microscopic world is deeply indebted to Mr. Wenham; but he very liberally awards me a share in the merit; for, in a letter to me, he says:—”Whatever I may have done in the invention, great credit is due to you for having started the thing, and brought it into notice; for, such would have been my own apathy, and that of the makers, that probably the only one ever made would have been that in my own possession. There is not one person out of a thousand that would have had the ‘pluck’ to order a thing of this kind that he had never seen!”

Mr. Wenham’s account of his instrument (in the January number) is so complete, that very little remains to be said in the way of explanation; nevertheless, I should like to add a few words for the benefit of those who may not perfectly understand why the last Binocular Microscope is so decidedly preferable to the former ones. Mr. Wenham has explained the reason to be that, instead of the whole light having to undergo prismatic refraction, as in the former instruments, one half is now simply transmitted in the usual manner; but probably very few, even of experienced microscopists are aware how very nearly the half of an object-glass comes up to a whole one in actual performance, especially in the lower powers. This is beautifully illustrated by an eclipse of the sun; for it has been truly observed, that though a total eclipse is everything, a partial one is nothing. Even when a full half or more of the sun’s disc is concealed, no one would suppose, from looking at the prospect around him, that anything was wrong with the sun. This may also be shown in the case of “the combined binocular and single microscope,” by the following experiment.

Get some friend, for the first time, to look through the Binocular, having previously placed a small opaque disc beneath the cap of the left-hand eye-piece, the prism being withdrawn. He will then see the object, whatever it be, in the usual way; and will probably say, “Beautiful!” “splendid!” or words to that effect. Then, while he is looking, with an instantaneous touch of the finger you slily pop in the prism. “Now, how does it look?” he will probably say. “Oh! just the same; unless that I think you have slightly altered the light.” “True; but you see every part of the object as well defined as before?” “Yes, quite as well; and I should say even more agreeably, for I fancy there is not quite such a glare of light.” “Ah ! then you will not readily believe that I have actually cut off one half of the entire disc of the object-glass.” “You don’t say so!” “Perfectly true, however.” The next step is to remove the opaque disc, and, for the first time in his life, submit to his astonished gaze — BINOCULAR VISION ! the double ray uniting in the cerebrum, to form one distinct and beautiful image, exhibited, moreover, with the most marvellous stereoscopic effect!

I assure you it actually compels people to shout with amazement! ! “Well, I never beheld anything equal to that! It is most magnificent! I seem to see part behind, part in real perspective !” (This effect, by the way, is admirably shown by a good specimen of hypersthene, with a 1-inch objective and Lieberkuhn reflector.) Now, the best part of the practical joke remains. After allowing your friend to luxuriate for some time over this gorgeous spectacle, and while he is still earnestly gazing, at it, you suddenly withdraw the prism; when he will probably as suddenly withdraw his head, exclaiming, “Dear me ! how is this? Why, I appear suddenly to have lost half my eyesight. How very unpleasant! What have you done ?” “Done, sir; why, I have merely brought back the microscope suddenly to its ordinary state. Can you, now, believe it?—that is really the way you have been using the instrument all your life !”

And now a few parting words on another topic. My last communication on the above subject was, by some trifling editorial inadvertence, I suppose, headed “Further Notes on Finders;” which, I have been informed, puzzled a good many. But I must take the present opportunity of confessing my error in supposing myself like Columbus (No. xxxii, p. 201), for I have since had the mortification of finding myself forestalled; for the “double nose-piece” is recommended as a finder by Dr. Carpenter, in his excellent work, ‘The Microscope and its Revelations/paragraph 51. I was utterly unaware of this when I sent the communication, No. xxxii, p. 198. But I do not regret having done so, as it has been the means of drawing the attention of many to the subject. Moreover, every microscopist may not have a copy of the said work, though every one ought. My opinion still remains the same. The Maltwood finder works tolerably up to one eighth; but, with a sixteenth (which I chiefly use with the Diotomaceous tests), the figures become so fearfully diluted and nebulous that they require a finder, i. e., lower power, to find them !

I have recently discovered another useful application of the nose-piece. It does admirably for comparing two achromatics of the same power, in order to ascertain which is the best. The ordinary tedious mode of screwing and unscrewing is very objectionable, as so much time is lost that the observer cannot satisfactorily bear in mind the two effects. With the nose-piece the change is made in an instant; both are brought, as we may say, close together, and may thus be very accurately estimated.

In this way I have been carefully comparing two recent inch achromatics by two of our first makers; and the result is, that no perceptible difference can be detected: which shows, by the way, how wonderfully our opticians work up to each other. On the other hand, if we thus compare an achromatic of the present day with another of the same power and maker, but constructed, perhaps, only a year or two ago, it strikingly shows the rapid improvement made in achromatics; every slight alteration of curve, density of glass, variation of combination, &c., having been productive of more or less benefit. When shall we get to the top ?— HENRY U. JANSON, Pennsylvania Park, Exeter.

Binocular.—In answer to numerous private inquiries for advice, and a recommendation of the makers who will apply my binocular adaptation to microscopes generally in the best and most efficient manner, I have to state, that after a careful examination of the instruments of the three who have, up to this time, professed to construct them, I can pronounce the definition of the binocular arrangement equally good in all; and as each is determined in making the new instruments as perfect as possible, I feel assured that I cannot do better than strongly recommend parties requiring their instruments to be altered to send them to the original makers, who will certainly be best qualified for applying the binocular arrangement to their own particular instruments. I am sure this will be most satisfactory in the end to microscopists, as well as the opticians, and prevent the possibility of any invidious comparisons being set afloat at the expense of other instruments, for the purpose of obtaining business by a self-assumed superiority of construction; a course of proceeding, which, I take it for granted, none of the opticians with whom I have at present the pleasure of being acquainted would wilfully pursue.—F. H. WENHAM; March 20th, 1861.

The Royal College of Physicians of London is about to open its halls for evening instruction. A short course of lectures on the Structure of the Tissues of the Human Body, with observations on their growth, nutrition, and decay, is announced for delivery by Dr. Lionel Beale, the Professor of Physiology at King’s College. These lectures will be delivered on Monday evenings, at half-past eight o’clock, commencing on Monday evening, the 8th of April. It is very gratifying to find the College of Physicians thus endeavouring to meet the spirit of the age, and it is to be hoped that such encouragement will be given to this course of lectures as to induce some of the other distinguished members of that body to give the result of their experience in the form of short courses of lectures.