6. It should be simple, strong, and durable. Mobility and constant readiness for action are indispensable with cavalry, while lightness and smallness of target are essential factors. There are eight main types of machine guns at present in use in the armies of the world, viz.: Gun. In use in Maxim Great Britain, Germany, Russia, Italy, Portugal, Turkey, Switzerland, and U.S.A. Hotchkiss France, Japan, Belgium, Norway, Sweden, Spain, and Portugal. Perino Italy. Puteaux France. Schwarzlose Austria. Skoda Japan and China. Madsen Russia, Denmark (Rekyl pattern), and China (for cavalry). Colt By several countries in addition to adopted gun. The principal differences between these guns are: (_a_) The automatic mechanism. (_b_) Method of loading. (_a_) may be divided into two classes: 1. _Recoil action_--the Maxim, Perino, and the Madsen. 2. _Gas-pressure action_--the Schwarzlose, Hotchkiss, Skoda, and Colt. (_b_) consists of three classes: 1. _Belt loaders_--the Maxim, Schwarzlose, and Colt. 2. _Metal clip loaders_--Hotchkiss, Madsen, Perino, and Puteaux. 3. _Hopper loaders_--the Skoda. Several of the above countries--notably Russia, Japan, France, and Austria--have more than one pattern of gun in their service, and it is difficult to say which they intend finally to adopt; but Russia, since the war, has ordered several thousand Madsen guns, and Japan is said to be trying this gun, one of which during the war fired 25,000 shots in a single day. The Rexar gun has been purposely omitted; it only weighs 17½ lb., but is fired from the shoulder, and is therefore more of the nature of an automatic rifle than a machine gun. It would take too long to deal with each of these weapons separately, therefore the Maxim has been selected as the type with which to discuss the question of tactics.