In this class of submarine offensive machines may be placed the following:-- 1.--Harvey's towing torpedo. 2.--Menzing's towing torpedo. 3.--The French towing torpedo. _Harvey's Torpedo._--This form of towing torpedo was invented conjointly by Captain John Harvey and Commander Frederick Harvey, R.N., and is intended to be used at sea both as a means of offence and defence. At Fig. 104 is shown in elevation the small sized Harvey towing torpedo, in which all the latest improvements that have been devised are represented. _a_ is the case of the torpedo, formed of Muntz's metal, but not provided, as the original ones were, with an exterior case of wood; by this alteration greater capacity combined with extreme lightness is obtained, which undoubtedly much enhances the value of the small size torpedo which is intended to be carried by and manoeuvred from boats; _b_ is the principal or after lever, hinged on the top of torpedo at _c_, and rests, when ready for action, in a crutch formed in the top of the exploding bolt _d_; _e_ is the foremost lever, hinged at _f_, and kept in position on the after lever _b_ by a groove formed in it and a lashing which passes through a slot in the principal lever, as at _g_; _h_ is the side lever, pivoted at _i_, and exerting a pressure on the firing bolt _d_ by means of a lanyard which is passed through the bolt _k_ and over the principal lever _b_; _l_ is the top lever, pivoted at _m_, and exerting a pressure on the bolt _d_ by means of a lanyard which is passed through the bolt _n_ and over the principal lever _b_; this top lever _l_ has been added to ensure the action of the torpedo, on its striking sideways against a vessel; _o_ and _t_ are handles, to the former of which the lashings of the levers _h_ and _l_ are secured; _p_ is the ring used for attaching the buoy rope; _r_, _r_ are two loading holes, made in the side of the torpedo case, by which a charge of gun-cotton may be quickly and efficiently stowed; this also is a new feature in the small size torpedo; _s_ is the rudder formed for the purpose of controlling the direction of the torpedo when the tow line is suddenly slacked. In regard to the large size torpedo, the construction of the case remains as in the original ones, the improvements being, the enlargement of the loading and fuze holes, and the addition of the top lever _l_, as shown at Fig. 104. The small size torpedo is capable of holding 47 lbs. of water, whilst the large size one will contain 76 lbs. of water, or about 33 lbs. and 58 lbs. of gun-cotton respectively. The slings are made of best Italian hemp, and consist of a span of four legs, which are secured to lugs at the corners of the torpedo and connected to an iron thimble, which is shown at Fig. 105; this thimble is made suitable for either wire or hemp rope, and is so arranged that should the seizing become slack, the parts of the slings cannot become detached from the thimble.