2. Open the plate and rest one edge of the cover-slip on the surface of the medium a little to one side of the selected colony. Lower it cautiously over the colony until horizontal. Avoid any lateral movement or the inclusion of bubbles of air. 3. Make gentle vertical pressure on the centre of the cover-slip with the points of the forceps to ensure perfect contact with the colony. 4. Steady one edge of the cover-slip with the forceps and pass the point of a mounted needle just under the opposite edge and raise the cover-slip carefully; the colony will be adherent to it. When nearly vertical, grasp the cover-slip with the forceps and remove it from the plate. Re-cover the plate. 5. Place the cover-slip, film uppermost, on the rubber mat, and cover it with an inverted watch-glass until dry. 6. Fix by immersing in one of the fixing fluids previously mentioned (_vide_ page 82). 7. Clear with acetic acid and alcohol. 8. Stain and mount as an ordinary cover-slip film preparation, being careful to perform all washing operations with extreme gentleness. ~Microscopical Examination of the Unstained Specimens.~-- 1. Place the body tube of the microscope in the vertical position. 2. Arrange the hanging-drop slide on the microscope stage so that the drop of fluid is in the optical axis of the instrument, and secure it in that position by means of the spring clips. 3. Use the 1/6-inch objective, rack down the body tube until the front lens of the objective is almost in contact with the cover-slip--that is, well within its focal distance. This is best done whilst bending down the head to one side of the microscope, so that the eyes are on a level with the stage. 4. Apply the eye to the ocular and adjust the plane mirror to the position which secures the best illumination. 5. Rack the condenser down slightly and cut down the aperture of the iris diaphragm so that the light, although even, is dim. 6. Rack up the body tube by means of the coarse adjustment until the bacteria come into view; then focus exactly by means of the fine adjustment. Some difficulty is often experienced at first in finding the hanging drop, and if the first attempt is unsuccessful, the student must not on any account, whilst still applying his eye to the ocular, rack the body tube down (for by so doing there is every likelihood of the front lens of the objective being forced through the cover-glass, and not only spoiling the specimen, but also contaminating the objective); but, on the contrary, withdraw his eye, rack the tube up, and commence again from step 2. ~Dark Ground Illumination.~-- 1. Set up the microscope stand in the vertical position and insert the highest eyepiece available. 2. Remove the nosepiece from the microscope tube and fit the 2/3 inch objective in place. 3. Remove the substage condenser and replace it by the dark ground condenser.