PROCEEDINGS OF THE SOCIETY.

MEETING OF 9TH OCTOBER, 1878, AT KING'S COLLEGE, STRAND, W.C. THE PRESIDENT (H. J. SLACK, ESQ.) IN THE CHAIR.

The Minutes of the meeting of 5th June were read and confirmed, and were signed by the President.

A list of the Donations since the last meeting was submitted and the thanks of the Society given to the donors.

The President said they had the pleasure of seeing amongst them that evening Professor Owen, who was their first President, and who had come to read a paper which he had sent to the Society.

The President said they would no doubt all remember that some time ago, Mr. McIntire presented to the Society a slide of the perforating proboscis of a moth, and in connection with it they would also remember that reference was made to a paper in Comptes Rendus' which described at some length a moth which possessed a similar perforating organ, and was reported as doing damage to oranges. A few days ago, he had received from Mr. Green of Colombo, through Mr. Curties, a specimen of a moth which was also able to perforate oranges in a similar manner, and it was described as hanging on to the fruit by means of the proboscis whilst it sucked the juice. On examining this proboscis, he found that it differed somewhat from those which had been described, in that it possessed a peculiarity which he hoped Mr. Green would work out. It seemed that the proboscis was armed with a series of cutting hooks, having cutting edges on both sides, thus enabling the insect to cut its way out as well as to cut a way into the fruit. At the base of these hooks or spikes was an organ which looked as if it might be a ball-and-socket joint, and the spike appeared to pass down to its attachment with this through a countersunk orifice, which enabled the spike to move through a large angle, and when extended would of course assist the creature to hang on in the manner described. He hoped that the attention of those of their friends who might be living in orange-growing districts, would be called to the matter with a view to ascertain if there were any other moths of this kind to be found, which might form an intermediate link between the two kinds already observed, and which presented very distinctive characters.

Figures in illustration of his remarks were drawn upon the blackboard by the President as he proceeded.

Professor Owen, C.B., F.R.S., &c., then read a paper "On the Fossils called 'Granicones,' being a contribution to the Histology of the Exo-skeleton in Reptilia," illustrating the subject by a number of drawings, and by sections exhibited under a microscope (the paper will be found printed in extenso at p. 233).

The President, in proposing a vote of thanks to Professor Owen for his paper, said that all would feel the interest it possessed, although as the subject was quite new it was hardly possible for any discussion now to take place upon it. He was sure that the Fellows would not only thank the Professor for his paper, but would also join him in saying that they were specially glad to be able to give him a personal welcome on account of his long connexion with the Society.

A vote of thanks to Professor Owen for his paper was unanimously passed.

Professor Owen said that it might be familiar to them all that so many of the fossil remains which were found in the Mesozoic strata -both of animals, plants, and shells-belong to a class of which the nearest living representatives are now found at the antipodes. Those beautiful specimens containing the well known teeth of Cestracion were well known, and there was still living in Australia a creature exhibiting the same kind of dentition and which was described as going along the reefs and picking off the Terebratulæ and crushing them between these teeth. The evidences as to the Stonesfield slate and similar formations, showed that all the individuals forming the group found there were Marsupials, the only living representatives of which class are now found in Australia. He had often been disposed to say, that the further they had to go in the strata for their fossils the further afield they had to go in the world for their present representatives; thus these things which had been puzzling him for so long were at last found to belong to a class of creatures which were only now represented by the horrid little lizard in Australia, Moloch horridus.

Mr. Crisp (Secretary) read a communication by Colonel Woodward, entitled "Further Remarks on a 'Simple Device' for the Illumination of Balsam-mounted Objects for Examination with Immersion Objectives whose Balsam Angle is 90°" (see p. 246), previously reminding the meeting of Colonel Woodward's first paper on the subject which appeared in the M. M. J.' of August, 1877. The original apparatus as there described, and the two prisms referred to in the further remarks, were placed on the table for examination.

He also read extracts from a letter from Colonel Woodward, stating that "he hoped to have something to say to the Society in the autumn about the treatment of A. pellucida in balsam by objectives of moderate power, but excessive angle amplified to high powers. To illustrate the possibilities of the method, he had sent a paper print of A. pellucida in balsam as shown by a Spencer duplex, of rather more than 110° balsam angle, amplified so as to give equal powers with equal distances to those given by Powell and Lealand's. The whole frustule shown on the print was 0038 of an inch long, so that the magnifying power obtained was about 2420 diameters, and he thought it would be said, with very little distortion and good resolution of the lines from end to end. The striæ on this frustule were, as would be seen by counting the number to the inch and multiplying by the magnifying power, about 100 to the Too of an inch, so that

the test was sufficiently difficult. On the whole, the result seemed to him quite satisfactory, but there was a certain muddiness in the picture, due to the use of an old amplifier which needed repolishing. He was having some new amplifiers made with which he expected to get more sparkling pictures."

The photograph accompanying the letter was handed round for examination; it showed the stria with remarkable distinctness.

Mr. Ingpen inquired if any question as to priority in regard to the invention or use of this prism arose out of the paper. He had himself seen a prism with four faces, made by Messrs. Powell and Lealand, from drawings by Dr. Edmunds, which appeared to more than cover the ground aimed at by the prisms now shown.

Dr. Edmunds, in reply to a question from the President, said that, as to the prism to which Mr. Ingpen had referred, he had not thought it of sufficiently marked novelty to make it the subject of a formal communication, but he would be pleased to submit it to the next meeting. Upon the question of priority, it would be recollected that in 1856 Mr. Wenham described a small right-angled prism, which he attached to the under surface of the slide with oil or balsam, and used for oblique illumination. This application of a right-angled immersion prism was clearly due to Mr. Wenham. What was due to Colonel Woodward in his beautiful work was not the invention of the right-angled prism, but its combination with a pin-hole shutter, through which a small beam of parallel light could be thrown into a balsam-mounted object outside the angle of 41° from the optic axis; thus demonstrating that pencils outside 82° balsam-angle could be used to form an image if only the objective were of sufficiently large aperture. With reference to his own prism, he had had the advantage of working with that sent over by Colonel Woodward, and finding it difficult to manage, and that its corners practically prevented its rotation under the slide, he had had another form constructed by Messrs. Powell and Lealand, and this had proved most useful and very easily managed. It was made from rather more than a hemisphere of glass, of which the spheroidal surface was ground down into four faces making practically two right-angled prisms at right angles to each other, one having its faces inclined to the plane surface at 41° and 49°, and the other at 30° and 60°. The prism was set in a simple brass tube with a slot for each face, and fitting below into the substage. The faces were so arranged that an object in focus was illuminated equally through each face by light entering it at the normal. The upper surface was inch in diameter and was made optically continuous with the slide by oil or glycerine. By simply turning the substage, the prism gave unrefracted light at 30°, 41°, 49°, and 60° from the optic axis, and each angle could be varied a little without practical detriment. The light reflected from the top surface of the prism passed out through the other side at the normal, and thus glare was prevented. The prism worked charmingly.

Mr. Crisp said that the interest of Colonel Woodward's present apparatus arose entirely out of the angle of aperture discussion. Colonel Woodward certainly had never claimed and did not intend to

claim the invention merely of a right-angled prism for illuminating objects under the microscope, but obviously the particular application of such a method for the special purposes dealt with by his paper. As Dr. Edmunds had said, the right-angled prism was undoubtedly not 66 new"-indeed it had become very difficult to substantiate a claim to actual novelty as regards the mere form of any illuminating apparatus, as things seemed to be re-invented over and over again in more or less regular cycles. Mr. Wenham, who was admittedly the "first and true inventor" of the right-angled prism, used it, however, entirely for the illumination of objects under high powers by total internal reflection from the upper surface of the covering glass. Those curious in the matter would find a summary of the various analogous devices of Mr. Wenham and others in the second German edition of Harting's 'Das Mikroskop,' the figures in which he showed to the meeting. Canada balsam or other medium was interposed between the prism and the slide in Mr. Wenham's arrangement for the purpose of preventing the rays from being reflected from the back of the prism instead of passing on to the covering glass.

Mr. Crisp (Secretary) said that a Congress of American Microscopists had been held in August at Indianapolis, at which the subject of a "Unit of Micrometry" had been taken into consideration, and he read the Resolutions which had been passed by the Congress recommending the use of the T of a millimetre (see p. 254).

Mr. Beck inquired if it was intended to take any action with reference to the Resolutions. The desirability of a uniform standard had always been appreciated in this country, and it would be a very desirable thing if the Society would now give the weight of its influence towards the establishment of such a standard. Some time ago the adoption of a single thread for the screws of all objectives was due to the action of the Society, and though perhaps the one decided upon might not be the best, yet the adoption of a uniform gauge had been of very great advantage in the way of getting rid of those horrible nuisances, the adapters. He merely threw out the suggestion because he thought the idea was worth their consideration, and he should like to know whether or not the Council were prepared to take any action in the matter.

Mr. Crisp added that at the Congress a paper had been read by Professor W. A. Rogers, of Harvard University, in which it was understood that he had explained the application of a machine he was using for the production of "standard" micrometer scales, and by means of which he believed that he could rule any number of micrometers precisely alike and with exceptional accuracy. It should not be forgotten that, as Mr. Reeves reminded him, the subject of a uniform micrometric standard had been very completely dealt with by Dr. Cooke in a paper read before the Quekett Microscopical Club, and printed in their Journal on p. 1 of vol. i.

Mr. Beck, in reply to the President, said there would be no difficulty whatever in obtaining scales ruled as required for the adoption of the proposed standard.

Dr. Edmunds thought that the whole question of microscopical measurements wanted going over and revising. It had been said that there was a Society's screw for objectives, but when he wrote to the Assistant-Secretary to ask him for a standard gauge, he was told he could not be supplied, and so he found that his mounts of Powell and Lealand's would not fit Ross's, and that Smith and Beck's again differed from these.

Mr. Beck said, there certainly was a standard in the possession of the Society, which was made by Whitworth at the time the question was settled, and there could be no doubt that by applying to Whitworth they could get others so exactly the same that all made to it must accurately fit one another. The differences now complained of were owing to makers not having revised their screw tools from time to time, so as to ensure that they were accurate.

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Dr. Edmunds said that there were also other questions that should be pronounced upon by the Council. For instance, what is the "10-inch" tube? In practice the length varies with each of the makers, and the eye-pieces are so constructed as to destroy all uniformity in the datum point at the eye end of the tube. Practically the end of the tube measured from the diaphragm in the eyepiece. Nevertheless the 2-inch eye-piece-one of the chief makers only excepted-was shouldered about an inch beyond its diaphragm. On the other hand the -inch eyepiece necessarily has its shoulder about on a level with its diaphragm. It followed that in changing the 2-inch eye-piece for the -inch the optical tube was lengthened no less than an inch. Therefore the amplification given by the objective at the point where it was taken up by the eye-piece, was greatly increased while the objective itself needed to be readjusted, and to have its focus shortened before it was fit to be viewed by the -inch eye-piece. Yet all this could be remedied by the simple plan of shouldering the eye-pieces on a level with their diaphragms. Then again, why should not the visual and substage tubing of the large microscopes always be of the same size? At present several of the chief firms made their substage tubing different in gauge from their own visual tubing, and consequently the eye-pieces could not be used for condensers. Nor was there any adequate reason why all the large microscopes, and on the other hand, all the small microscopes, should not be made to a standard gauge, so that apparatus made by various makers could be used indiscriminately.

The President said that as to the standard of the Society's screw, that was carefully kept in the possession of the Council, and copies could no doubt be obtained from Whitworth if they were required. With regard to the present discussion, it would be understood that Mr. Beck would be kind enough to give them his ideas on the subject of micrometric measurements, and that Dr. Edmunds would similarly undertake the other questions as to size of screw, tube, &c.

A letter was read from Mr. F. Habirshaw, of New York, in reply to one addressed to him by Mr. Crisp in reference to the discussion that had recently taken place on the "Revification of Diatoms," and particularly the note on p. 150, in which Mr. Habirshaw said,