244 report — 1859. 



Every yard of the chain passed over the pulleys representing a yard of space that 

 the boat has progressed in her course — the fixed point or length of chain lying at 

 the bottom of the canal still remaining the same, what is taken up at the stern being 

 replaced by exactly the same length deposited at the bows. The speed of the vessel 

 is thus exactly equivalent to the speed and size of the driving pulleys, unless, indeed, 

 there should be any slip of the chain in passing over them, and this in practice is 

 easily prevented, and is again exactly measured by the velocity of the chain, unless 

 there should be a slip of the chain along the whole length over the bottom of the 

 canal, and this, of course, is a mere matter of the weight of the chain. 



On the Nomenclature of Metrical Measures of Length. 

 By G. Johstone Stoney, M.A., M.R.I.A. 



In this paper many circumstances were pointed out which render the French names 

 of decimetre, centimetre, and millimetre unsuited to this country. They are foreign 

 to the genius of our language, which delights in short pithy words ; the information 

 they convey is useless, as the fact that each measure is one-tenth of that above it is 

 one of that class which it is impossible to forget, and they fail in several common 

 requisites of a good nomenclature. 



Names of measures for ordinary use should, if possible, be monosyllables; for the 

 convenience of reference they should begin with different initial letters; they should 

 so wholly differ in sound that even when imperfectly pronounced they could not be 

 mistaken for one another, and they should convey some information which would 

 facilitate the use of the measures by those who are unfamiliar with them. 



To combine these advantages, it was suggested that hand or hand-breadth should 

 be used as the English equivalent for decimetre, nail or nail-breadth for centimetre, 

 and line for millimetre. The author stated that he had had abundant experience of 

 the assistance afforded to beginners by these names, from their promptly suggesting, 

 without any mental effort, the absolute length of each measure. 



Attention was also directed to the importance of giving a distinct name to the 

 tenth part of the line or millimetre, in order to discourage the use of binary subdivi- 

 sions : mite was suggested as a suitable name. 



The paper closed by urging that the use of foot-rules graduated along one side to 

 metrical measures should in every possible way be encouraged. 



On the true Action of what are called Heat-diff users. By A. Taylor. 

 Gases do not radiate the heat which they contain ; so that the only mode in which 

 a gas can communicate its heat to a surface is by contact or conduction : this in 

 the present practice is the only mode in which the heating surfaces of a boiler which 

 are not exposed to the radiation of the fire or flame can abstract heat from the pro- 

 ducts of combustion : but if in a flue or tube a solid body be introduced, it will 

 become heated by contact with the gases, and will radiate the heat thus received to 

 the sides of the flue. It will be admitted that the amount of heat thus conveyed to 

 the water may be very important, when it is considered that the temperature of the 

 gases in the tubes of a boiler at five or six inches from the fire-box tube plate is 

 about 800° Fahr., and that these radiators will consequently have a temperature of 

 several hundred degrees above that of the surfaces in contact with the water in the 

 boiler, and that a very active radiation must consequently take place from one to the 

 other. This principle once established, the modes of application in practice are of 

 course endless. It is, however, unnecessary to make the radiating surfaces of such 

 a form as to impede the draught. I would rather choose the form which would 

 give the greatest amount of radiating surface and offer the least impediment to the 

 free passage of the products of combustion through the tubes. Perhaps as effective 

 a form as any for placing in the tubes of boilers would be a simple straight band of 

 metal, or a wider band bent in the direction of its breadth at an angle of 60° thus — 

 (D© In the case of marine boilers, they should be made to draw out easily 



to enable the tubes to be swept. 



Description of various Models of Fire Escapes, Boat-lowering Apparatus, fyc. 



By Adam Topp. 



