of Steam-Power Ifi Navigdtimi 9!^ 



relatively to that power. Without masts, and towed, as I thinir it oUghl 

 to be, close uji in the smooth wake, and under the lee of the tug, feven 

 under the most unfavouralde circumstances a vessel of this description 

 will tow light. In America it was on one occasion ascertaincil, that to 

 give a vessel a certain velocity, one-third only of the power la required 

 if that power is ajjplied from without, to what is necessary if it is em- 

 barked in the vessel herself. At the mouth of the Tyne, where steam- 

 towing prevails to a great extent, steam-boats down to three-horse powers 

 take charge of colliers in light weather, and tow them oiit to sea over 

 Shields' bar ; while the highest average power employed is about thirty -six 

 horses, and this takes them out against any weather, with their masts and 

 yards up, and heavily laden. And every seaman who has had occasion to send 

 his boats ahead to tow in a calm, must have been astonished at the effect he 

 thus produced, if he ever considered the unfavourable line of traction, ge- 

 nerally from the bowsprit end and consequently deviating greatly from the 

 horizontal, — the petty lever, a few boats* oars, employed, — and the certain 

 nullity of the same power, had he used it on board. There can be no doubt, 

 then, that a very small power, relatively, will here produce a great effect *, 

 particularly if other circumstances are kept favourable too. The vessel towed 

 should also be flat, and studiously modelled to tow light,— in particular per- 

 haps, lightly timbere<l, with her extreme breadth well forward, tapering otf to- 

 wards the stem in a straight line, and sitting at least on an even keel, or ra- 

 ther a little by the head,— this being the sit of a mast with its large end 

 foremost, in which way it is found to tow lightest. That the greatest capa- 

 city may be joined to the smallest size, her hold should be kept entirely clear 

 for cargo, the crew and passengers being accommodated on deck ; and on the 

 poop and forecastle thus erected, and further supported by a narrow platform 

 between them, the requisite spars and rigging to enable jury-masts to be 

 stepped, and a little sail made on occasions, might be stowed away. Two ex- 

 tra half keels, the same as on the tug, will at once give her stability on these 

 occasions, keep her to windward, and prevent rolling ; like the vessel herself, 

 they should taper off towards the stem, and, if constructed to slide up and 

 down, according to circumstances, on Admiral Schank*8 plan, there would 

 be an advantage. The mode of connecting the two vessels will be best de- 

 tailed subsequently under the head of Tactics. In the mean time, supposing 

 all difficulties of that kind can be overcome, provided there is sufficient mo- 

 tive to induce us to make the attempt, let us now inquire what is then the 

 motive, and to what extent this would seem to be an improvement on the 

 current means, especially of mercantile communication. 



« This is another portion of the subject, at the saiue time, on which a few well arranged ex- 

 periments on A great scale would be very desirable. The particular result alluded to above as 

 obtained by the Americans, was, « that to give a vessel ascchdU^ the Mtatelppl an alMolutc ve- 

 locity etiual to oiie-half the current of that Hver," (which by other oqicrfanents was found the 

 most effective pace), " three times the powar was required If embariad on board of her, to what 

 was necessary when cmployetl on shore tracking her." But the general questions would be. How 

 far Is this advantaRC maintained, lost, or increased, when the tugging force is also afldat ? Does k 

 differ materially at different rates of velocity, or In diflbrent states of WMAher, or when the power 

 and the weight to be transiK>rted arc otlicrwlse In dlfibrent proportknt f If ao, what are the most 

 advantageous rates and proportions for towing> and carrying \ dec. 



