NATUKAL PHILOSOPHY. 195 



Judge Osborn gave some curious circumstances about sand-blasting. Tho 

 hole is not to be entirely filled, and the sand should be dry. Dry chaff may 

 be substituted for sand, and would be better than wet sand. At an explosion 

 he noticed that those who were furthest from the explosion were thrown 

 furthest and least injured. The nearer ones were moved little, but denuded 

 and mangled. 



OX MECHANICAL NOTATION. 



The following paper on the mechanical notation to be used in describing 

 machinery, was read before the British Association, Glasgow Meeting, by Mr. 

 Babbage. The method proposed is one of great importance to all engaged in 

 the construction and description of machinery, since without the aid of 

 mechanical notation it would be beyond the power of the human mind to 

 master and retain all the details of complicated machinery. 



" To understand the construction of a machine, we must know the size and 

 form of all its parts the time of action of each part and the action of one 

 part on another throughout the machine. The drawings give the form and 

 shape, but they give the action of the parts on each other very imperfectly, 

 and nothing at all of the tune of action. The notation supplies the deficiency, 

 and gives at a glance the required information. Having made the drawings 

 of a machine, we must assign letters to the different parts. Hitherto, I 

 believe, this has been left to chance ; and each one has taken the letters of 

 the alphabet, and used them with little or no system. "With respect to letter- 

 ing-, the first rules are, that all framework shall be represented by upright 

 letters. Movable pieces shall be represented' by slanting letters. Each 

 piece has one or more working points each of the working points must 

 have its own small letter the working points of framework having small 

 printed letters, and the working points of the movable pieces having small 

 written letters. We have the machinery divided into framing, indicated by 

 large upright letters ; movable pieces by large slanting letters ; working 

 points of framing indicated by small printed letters; working points of mova- 

 ble pieces indicated by small written letters. In letter drawings the axes are 

 to be lettered first. Three alphabets may be used the Roman, Etruscan, 

 and written. These should be selected as much as possible so that no two 

 axes which have arms or parts crossing each other shall have letters of the 

 same alphabet. Having lettered the axes, all the parts on them, whether 

 loose or absolutely fixed to them, must be lettered with the same alphabet, 

 care being taken that on each axis the parts most remote from the eye shall 

 have letters earlier in the alphabet than those parts which are nearer. It is 

 not necessary that the letters should follow each other continuously, as in the 

 alphabet ; for instance, D, L, T. may represent three cog-wheels on the same 

 axis; D must be the most remote, L the next, and T the nearest. The rule is, 

 that ' on any axis, a part which is more remote from the eye than another, 

 must invariably have a letter which occurs earlier in the alphabet.' By this 

 system very considerable information is conveyed by the lettering on a draw- 

 ing ; but still more to distinguish parts and pieces, an index on the left hand, 



