Dr. Carpenter found large areas of very low temperature in the temperate and inter-tropical zones co-existent with high-surface heat. The fauna of these cold areas in low latitudes corresponded precisely with that found in Sir E. Parry's soundings from Arctic Seas.

When the bottom temperature was high the fauna changed its character, the Cretaceous formation going on in warm localities, while in close proximity the greensand is accumulating under privation of heat. With the increase of our knowledge of the forms of life satisfactory theories respecting its means of sustenance have been offered; the lowest forms-mere atoms of living jelly-absorbing nourishment from the universally-diffused remains of surface life, and in their turn feeding higher organisms.

Carpenter found in the gases separated from deep water a constant increase in the quantity of carbonic acid where life abounded, and a corresponding decrease where it was scanty.

In the ocean, as on the land, food and oxygen-excretion and carbonic acid, are the conditions and consequences of life.

Mr. Hennah concluded by saying that it is impossible to overrate the importance of the discoveries recently made by Carpenter and others, and that he hoped the discussion would turn on them.

In the course of his report he mentioned the common Difflugia of our heath springs and streams as a convenient example of Arenaceous Foraminifera for examination in a living state.

[We much regret that, owing to extreme pressure on our space, several interesting reports of other Societies, though in type, are compelled to stand over.-ED. M. M. J.]

BIBLIOGRAPHY.

Sur l'Ovule et sa Nature morphologique chez le Primula sinensis, par E. Faivre. Lyon. Regard.

Histoire naturelle des Poissons, ou Ichthyologie générale. Par Aug. Duméril, Membre de l'Institut, Professeur administrateur au Muséum d'Histoire naturelle de Paris. Ouvrage accompagné de planches. T. 2, Ganoïdes, Dipnés, Lophobranches. Paris. Roret.

Études sur le Mécanisme de la Suppuration, soit: 1° note sur la suppuration étudiée sur le mésentère, la langue et le poumon de la grenouille; 2° note sur les phénomènes consécutifs à la stase veineuse observés sur la membrane natatoire de la grenouille et la possibilité de l'hémorrhagie par diapédèse (lues à la Société de Biologie, en mai 1869); 3° note sur le mécanisme de la suppuration (présentée par M. Vulpian à l'Académie de Médecine, le 25 janvier 1870); par Georges Hayem, aide d'anatomie pathologique à la Faculté de Médecine de Paris. Paris. Adr. Delahaye.

Leçons sur la Physiologie et l'Anatomie comparée de l'Homme et des Animaux faites à la Faculté des Sciences de Paris; par H. Milne Edwards. T. 9, 2o partie. Génération. Paris. Masson et Fils.

THE

MONTHLY MICROSCOPICAL JOURNAL.

AUGUST 1, 1870.

I.-On an Erecting Binocular Microscope. By J. W. STEPHENSON, F.R.A.S., F.R.M.S., Actuary to the Equitable Assurance Society.

(Read before the ROYAL MICROSCOPICAL SOCIETY, June 8, 1870.)

PLATE LVII.

BEFORE I describe the instrument which is on the table before me, it is perhaps desirable that I should briefly point out the purpose for which it was devised, without however dwelling on the great benefits which have unquestionably been derived from binocular vision when low, or moderately low, powers are used.

The inefficient working of the ordinary erector, when monocular instruments alone were known, became more obviously unsatisfactory when Mr. Wenham's beautiful invention was given to the world, for then, not only had we the optical defects and lowering of the magnifying power, which we had previously experienced, but we had in addition, whenever it became necessary to manipulate an object on the stage either in the way of dissection, selection or adjustment, to revert to the old form of instrument, and to make the change necessary in its optical arrangements in consequence, whilst the altered circumstances under which the object was viewed, not unfrequently rendered its recognition difficult, if not impossible.

My aim, then, has been to produce a binocular which, by inversion of the object, both laterally and longitudinally, shall act as an erector, and under which an object can therefore be dealt with without any change in the conditions under which it is originally

EXPLANATION OF PLATE LVII.

FIG. 1.-The two lower prisms, showing the division and lateral inversion of the cone of light on leaving the objective.

2. The upper prism, showing the longitudinal inversion of the laterallycorrected image.

3. The three prisms as arranged in use the two lower being rounded to fit into the arm which carries the object-glass.

4. The microscope in its entirety, rd of actual size.

VOL. IV.

F

Journal,

observed, whilst at the same time a horizontal stage is preserved, notwithstanding the inclination of the body of the instrument at any angle which by experiment may be found the most convenient in use the object of the latter arrangement being to enable the observer to dissect, or arrange, objects under fluids, a process which, with an inclined stage, is obviously impossible.

The former object is attained in the following manner.

The light emerging from the objective is received on the shorter sides of two truncated rectangular prisms (Fig. 1), of which the sides enclosing the right angles are equal; the hypothenuse planes of these prisms being placed together, but inclined to each other at an angle of about 4 degrees, form a wedge of glass, having an angle of about 94 degrees, and on this wedge the diverging cone of light falls. The light incident on the first surfaces (B C) of the prisms is thus divided, and being refracted towards the longer sides A B is thence totally reflected and emerges at the upper sides AD; the dispersion caused by refraction at the first, being corrected at the second transmitting

surface.

We have thus obtained two fields, each having, by one reflexion, been laterally inverted.

In order to perfect the erection of the image it is now only necessary to induce a second reflexion in a plane at right angles to the first, giving what I have called, for want of a better expression, the longitudinal inversion; this is readily accomplished by placing a third prism (Fig. 2) over those just described, and may be constructed to reflect the light at any angle which, as I said before, may be deemed the most convenient in use, although it is obvious that the nearer this approaches a right angle, the smaller will be the quantity of glass employed, and the less the consequent loss of light. It is sufficiently obvious from the figure that the two laterally corrected pencils of light entering the prism at BC are totally reflected at A B, and emerge longitudinally inverted at A C.

In the instrument before you this angle is 75 degrees (the others being of course 52 each), which is probably, with this stand, as convenient as any.

By the combination thus complete, the two perfectly-erected fields reach the eyes of the observer at an angle of 15 degrees (being the complement of that previously indicated), which enables him, with his arms resting on the table, to operate with fluids on a still horizontal stage, the distance of which, from the eye-piece, has been lessened rather more than an inch by the bent course which the light has been compelled to travel. At the same time the instrument, being perfectly symmetrical, the illumination of each field is exactly equal, and the focal distance the same.

Having thus imperfectly described the mode by which the two essential conditions have been fulfilled, I will now direct your at