ft6i4i Majoi -General Sir Howard Douglas o;t 



cwt. ; making the whole 35 cwt. The smaller, with its appur- 

 tenances, weighs only about 27 cwt*. 



The author gives accurate practical rules for determining the 

 depths to which either of the pontoons in our service will sink 

 in water when loaded with a given weight, and also conversely, 

 to find the weight of load corresponding to a given depth. From 

 these, a table is added, showing at once, by inspection, the 

 depths corresponding to given weights, which must prove very 

 useful to persons not conversant with intricate calculations, or 

 when an estimate of these must be made quickly for any special 

 purpose. The method of using this table (page 38), is exem- 

 plified by applications to infantry, cavalry, and guns. 



" The comparative powers of the two kinds of pontoons," the author adds, 

 (page 43), " are exhibited in the preceding pages ; from which it appears that, 

 with the same weight of infantry, the small pontoon is immersed 4 inches 

 more than the other ; and not being so deep by 3^ inches, the gunwales are 

 then only 6i inches above the water. Perhaps the adoption of a medium 

 size, as the only nature of a pontoon, would be preferable." 



The author then states the equipment of a full train of 36 

 pontoons, in four divisions, but which our limits will not admit 

 us to subjoin. 



In page 48, the method of laying a pontoon bridge is very 

 fully explained, and methods of determining the distance of the 

 opposite banks of a river clearly illustrated. The author throws 

 the investigation of some of his practical rules into notes at the 

 bottom of the page where they occur, and by this does not in- 

 terrupt the narrative. It would have been an advantage to 

 have given a formula and rule for the trigonometrical operation 

 also, though this may, in his opinion, be supposed to be derived 

 from works on trigonometry. In some of these that are really 

 adapted to practical men, a convenient rule or formula may be 

 found, though most of our ordinary treatises usually taught in 

 schools are remarkably deficient in these particulars. The fol- 

 lowing rule would have been convenient for this purpose. 



• To render these safe from the effects of shot piercing their sides, it would 

 be very convenient to have the interior cavity subdivided by tin traverses, so 

 that, though even one or two of the intermediate spaces were filled with wa- 

 ter, still the pontoon would not sink. To prevent the pontoons filling with 

 water, a tarpauling or canvass deck might be placed on such of them as were 

 most liable to such accidents. 



