. Machinery and processes of the industrial arts, and apparatus of the exact sciences. he same object, to present them in sucha manner that the axes of the eyes must be slightly inclined towardeach other in order to receive them. For this reason in part, but moreperhaps on account of the greater simplicity of construction, the well-known YTenham binocular, in which the division of the compoundpencil is effected by means of a trapezoidal prism, has met with moregeneral favor; and this form of the instrument has come extensivelyinto use in England and in this country. Mr. Cachet has recently int
. Machinery and processes of the industrial arts, and apparatus of the exact sciences. he same object, to present them in sucha manner that the axes of the eyes must be slightly inclined towardeach other in order to receive them. For this reason in part, but moreperhaps on account of the greater simplicity of construction, the well-known YTenham binocular, in which the division of the compoundpencil is effected by means of a trapezoidal prism, has met with moregeneral favor; and this form of the instrument has come extensivelyinto use in England and in this country. Mr. Cachet has recently introduced a binocular microscope of a muchsimpler description than his original one, which possesses the recom-mendation of being applicable to an ordinary instrument without alter-ing its construction or interfering with its usefulness as a monocular. NACHETS BINOCULAR MICROSCOPE. 539 An opening is simply made in the side of the body, immediately behindthe objective, into which is introduced Fig. 109. a rectangular prism carried in a mount- ing of metal, which reflects half the com-. pound pencil horizontally, and this isreceived upon another prism which drects it to the eye of the observer. Theinstrument, which is not particularlysightly, is represented in the figuresannexed. Fig. 109 is a view of the instrumeut with the parts united; Fig. 110shows the principal parts separate, andillustrates the manner in which the di-viding prism is introduced. In orderto accommodate the two tubes to thevarying distance between the eyes ofdifferent observers, the horizontal partcontaining the prisms was originallymade with sliders; but in the formwhich was exhibited in the Exposition,the extra tube has an angular move-ment around its lower extremity as aceptre. This involves the necessity ofa corresponding movement of the re-flecting prism at the centre of motion,to one-half the same angular Nachet has contrived an ingenious and simple combination of leversby which both movements a
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Keywords: ., bookcentury1800, booksubjectmachinery, booksubjectscientificappa
