The same object is obtained by the reflex type of camera in which the image formed by the lens is thrown upon a silver-faced mirror and reflected upward to the focussing screen. Focussing can be carried out, and a moving object followed till the moment when the exposure is made. The reflex type of camera is a trifle less bulky than the twin-lens, and, of course, only one high class and expensive lens is required. _A Focussing-cloth._—This is used for keeping out the light while focussing, being thrown over the camera and the head of the operator. It is generally made of black velvet, but waterproof sheeting is much better. It should have rings sewn on to one edge, or some arrangement by which it may be attached to the camera so as not to be blown away. _Camera-stand._—There are many varieties of tripod stands, with legs either folding or sliding into a small compass. For mountainous country it is of great advantage to have a stand with telescopic legs, as they can be readily altered in length so as to stand firmly on slopes or rocky ground. The smallest size, weighing about 3 lbs., and measuring 33 in. long when closed, and standing about 4 ft. 6 in. high, is steady enough to support a 6½ × 4¾ camera without perceptible vibration in a moderate wind. _A Small Circular Cup Level_, let into the wood of the camera, for levelling the camera on the tripod, is a useful addition. _Lenses._—There are many lenses in the market, and as it is impossible to do good work with an inferior lens, it is necessary to exercise great care in selecting this part of a photographic outfit. Lenses known as rectilinear or symmetrical are useful to a scientific explorer, and are well fitted for producing pictorial effect in his work. Ordinary portrait lenses are designed specially for rapid work, and this is attained at the cost of qualities in a lens most useful to an explorer. The so-called portrait combination should therefore be avoided. Rectilinear and symmetrical lenses give true images of objects to be photographed free from distortion, so that straight lines are reproduced as straight lines. In this way they are invaluable where accurate measurements have to be taken from photographs produced by them. [Illustration: HOMOCENTRIC LENS.]