[Illustration: Simple Dissecting Microscope No. 58a.] 58a. =Simple Dissecting Microscope=, consisting of a wood case with plate glass stage, movable plane mirror, two simple lenses of 4 and 8 times magnification. Price =2.--= 58b. =The same= with metal hand rests, moveable lens-holder and doublet magnifier No. 71, Price =3.50= [Illustration: Demonstration lens-holder No. 59. Focussing-lens Handle No. 61. No. 60.] 59. =Demonstration lens-holder=, consisting of a hardrubber stage with handle, clamps for holding the preparation in position, and with a moveable lens- holder. Without lens =2.40= 60. =Focussing lens= for photographic camera. Lens in spring-sleeve with clamping ring =4.75= 61. =Handle= with ring for holding lens =1.25= [Illustration: Steinheil lens No. 63. Steinheil lens No. 66.] The =aplanatic triplets after Steinheil= are remarkable for their large, flat field and excellent definition, free from chromatic aberration. Diameter Visual field Magnification 62. 24 mm 20 mm 8 diam. =4.--= 63. 15 " 15 " 10 " =4.--= 64. 12 " 12 " 12 " =4.--= 65. 10 " 10 " 16 " =4.--= 66. 6 " 3,5 " 20 " =4.--= 67. 5 " 2 " 30 " =4.--= 68. 3 " 1 " 40 " =4.--= The =achromatic doublets= have a very large, clear and flat field. 69. 30 mm 35 mm 5 diam. =4.--= 70. 23 " 20 " 8 " =3.25= =Doublet magnifier=, consisting of two double convex lenses. 71. 23 mm 25 mm 6 diam. =1.25= The doublet No. 69 can only be used as a hand lens. The mounting of all the other lenses is such that they fit any of the dissecting stands or lens holders. Aplanatic triplets 64-68 can only be used on stands with rack and pinion adjustment. [Illustration: Doublet No. 70.] [Illustration: Doublet No. 71.] [Illustration: Pocket lens No. 72.] 72. The aplanatic lenses Nos. 62-66 are also to be had with a moveable cover and ring adapting them for use as pocket lenses. Price, when thus mounted =4.75= [Illustration: Binocular Preparation Microscope.]