a height intermediate between that of the two figures seen laterally at the same time, in other words, between the left and right pictures of the diagram. This conclusion, it will be observed, corresponds, so far as vertical effect is concerned, with the observations of Prof. Wheatstone, cited on a previous page. 34. Limited range of the vertical compared with the horizontal power of combination. The details which have been presented indicate the narrow limits within which the power of vertical adjustment and combination is restricted as compared with those of binocular combination by ordinary convergence. Hence in combining figures which differ to the same extent in the horizontal and vertical directions, we generally find that while the coincidence on the right and left sides of the resultant is perfect and apparently simultaneous, the union at the top and bottom is but partial and is obviously successive. Indeed it is only when the disparity of heights is very inconsiderable that the combination appears to be equally complete in all parts of the resultant. 89. As an example of this, in attempting to unite the two squares of fig. 89, with the precautions as to adjustment before described, I find that while the vertical sides of the resultant figure appear each as a perfectly clear and distinct single line, the lower side appears double until the view has been fixed upon it for a sensible time and that on carrying the eyes to the top of the resultant this side also seems for a moment to be double. When however, the disparity between the heights is reduced to half the amount in the figure the upper and lower sides of the resultant present themselves in the shape of single lines as immediately and to all appearance as simultaneously as the vertical sides, and of course the resultant figure appears of a height intermediate between that of the right and the left hand figures. Like effects are exhibited by unequal circles and other pairs of figures geometrically similar. 35. Perspective position and usually warped figure of the resultant. We have seen in the preceding section that when figures of unequal horizontal breadth are united binocularly they form a resultant having an oblique or more or less perspective position. This effect must evidently occur in the case of unequal squares or circles or of any other figures differing in breadth as well as height. Thus when by cross vision I combine the squares of fig. 89 I see the left hand side of the resultant figure nearer to me than the opposite side, so that the whole has an oblique or perspective attitude either as a plane or concave surface. At the same time the near side appears shorter than the other as in cases previously explained, (fig. 44,) and thus the resultant of the two squares is visually a quadrilateral of unequal sides. In combining by the same process the two unequal circles. A... B, fig. 90, the left hand side of the resultant appears nearer 90. оо こ than the other and is concave while the other is convex, giving the figure an oblique position and a strangely warped appearance. This effect is made more striking if we combine the equal circles B.. C and the unequal ones B. . A in quick succession, in which case the oblique and twisted resultant of BA forms a marked contrast with the perfect circle which lying in a plane at right angles to the binocular direction results from the union of B and C. In the figure, the circles are placed at equal intervals in order that the same crossing of the optic axes may serve to effect both combinations and that the reader may have the advantage of comparing the resultants side by side. 91. When by cross vision we bring together the similar triangles A B, fig. 91, we observe towards the apex of the resultant a peculiar twist of the surface by which the right side is then thrown obliquely behind the other, and as we carry the view to the base of the figure and back again to the apex, the whole resultant takes the shape of a warped surface not unlike that of the mould board of a plow. By turning the diagram until the vertex of B is brought to the horizontal visual line the resultant is converted into a plane figure at right angles to the binocular direction, but containing the bases of A and B as separate parallel lines. A yet more remarkable flexion of surface is produced by combining the triangles of fig. 92, which are at the same time unequal and dissimilar, or by uniting the double set of unequal triangles forming fig. 93. 94. The association of unequal vertical rotation of the eyes with their ordinary converging adjustment occurs in viewing an object very much to the right or left of the medial line of vision. Thus when I hold a straight wire in a vertical position on the extreme left, and direct my view to the wall at some distance behind it, I see two unequal pictures of it on that surface as represented in fig. 94, the right hand or longer line being that proper to the nearer or left eye and the other that proper to the right eye. It is obvious that to see the wire single while in this position the same optical adjustments must be made as in uniting these two unequal pictures of the wire, and thus therefore vertical rotations differing for the two eyes either in amount or direction are as necessary in this case as in preceding experiments. In referring to the results of oblique vision as related to the union of unequal figures, Prof. Wheatstone remarks that "were it not for the binocular coincidence of two images of different magnitudes objects would appear single only when the optic axes converge forwards," &c. (Philos. Trans., 1838.) Sir D. Brewster on the other hand maintains that the apparent coincidence of unequal figures arises from an actual disappearance of one of them and that "in very oblique vision one of the eyes resigns its office and leaves the other to view the object distinctly and singly." (Phil. Mag., 1844). As regards the latter explanation I have before endeavored to show that the fitful vanishing and reappearing of parts of the figures often observed in these experiments is not directly connected with the development of the resultant (19), and that this latter actually includes both the components. In further support of this view, I would here adduce the fact, above proved, of the intermediate magnitude of the resultant figure. This seems to mark the visual perception as binocular, and not as the result of either impression singly, and to indicate that the two retinal images are equally concerned in the single perception which is produced. The sense of binocular direction attending these combinations is also in favor of this view. In respect to the conditions of the binocular coincidence perceived in these combinations, I conclude from the preceding ob servations that unequal vertical images or equal ones not correspondingly placed in the eyes do not of themselves and directly produce the single resultant perception, that the coincidence however seemingly simultaneous for all parts of the figure is really the effect of rapidly successive adjustment applied to the vertical and horizontal elements of the diagram, and that this process applied partially or throughout, according to circumstances, gives rise by suggestion, to the mental resultant. Other observations bearing on this subject are now in progresss more especially as regards the union of pictures seen in Dove's experiment by instantaneous or electric light, but they are not sufficiently matured to be communicated at this time. ART. XXIII.—Abstract of a Meteorological Journal kept at Marietta, Ohio, for the year 1855-Lat. 390-25'-Long. 4° 28' West of Washington City; by S. P. HILDRETH. January, February, March, April, May, June, 14 December, 33.66 35-23 65 12 12 19 2:50 s. w. & w. 30:10 28:45 1.65 8. & s. W. 29-60 28-90 70) 45 60 THE year 1855 exhibits a strong contrast to that of 1854, in several particulars, but more especially in the temperature, and amount of rain. Last year was noted for its excessive heat and great lack of moisture. The drought of the preceding year was continued into the following one. As late as the last of April and the first of May, people began to express their fears of another season of drought and heat which would in a manner ruin the country. The first four months affording less than nine inches of rain, an amount which has sometimes fallen in a single one. But in May, rain began to descend abundantly, so that in this and the three following months there fell nearly two feet, being twelve inches more than fell in the same months in 1854. Such a quantity had not fallen before in many years. This abundant supply had an astonishing effect on the crops. Wheat, Indian corn and grass sprang up with renewed energy, yielding an amount of produce unprecedented in the annals of Ohio. Wheat turned out, in some instances over fifty bushels to the acre. Indian corn on the uplands afforded as many bushels, as in ordinary years are grown on the rich bottoms; in one instance reaching the enormous quantity of one hundred and fifteen bushels. The stalks attaining a great height, even to twenty feet, loaded with ears, filled to their extremities with grain. This was the greatest growth known in the valley of the Ohio, and was in part occasioned by the preceding drought, pulverizing and warming the earth to an unusual depth, affording a loose mellow soil for the roots of plants to descend deeply, and thus acquire more food than usual. This light porous condition of the earth was noticed by all the farmers in plowing their lands in March and April. The meadows also yielded abundantly, but much of the hay was injured by excessive rains in July, with a lack of sunshine to cure it. A great quantity of wheat was sprouted or germinated, after it was cut and placed in shocks, before the weather would allow of its being stacked or put away in the barn. August was less wet, having only half the quantity of July-while September, usually a dry month, exceeded any other in the year, affording eight inches. The rivers, from early in the spring to the last of December, were in the best condition for boating, not lacking a sufficiency of water all through the summer and autumn. The great rains of September filled to overflowing the small rivers and creeks, causing much damage to the crops of corn and potatoes on the bottoms, a circumstance rarely if ever known before. Fruit of all kinds was abundant, especially apples and peaches. The grape crop was much injured by the excess of wet, many of the berries perished, leaving the bunches small, while the juice lacked saccharine material. It is a calamity, to which our vineyards will be liable in wet seasons, until the ground on which the vines are planted is deeply trenched and ameliorated by underground drainage. Sweet potatoes were abundant, of a good quality, but not so rich in sugar as in dry seasons. Irish potatoes were excellent in every respect. Beans, an important crop, along the Ohio river, were much damaged by the rains, affording not more than half the usual amount fit for market, occasioning a great advance in their price. Year.-The mean temperature of the year is 530.15, being 10.10 below that of 1854. The amount of rain and melted |