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THE FARMER'S MAGAZINE. 



outcry ; then, if you are to Lave an outcry, have it for some- 

 thing that will be worth the struggle — for sonuthini^ that is 

 really good — and that will arouse the zeal, and call forth the 

 energetic co-operation of the benevolent and well-informed. 

 Therefore, iu putting down bad local customs, put down at 

 the same time a bad national system ; and in making any 

 change, make it so that you shall not be called on to begin 

 your work over again as soon as it is finished. I may remark, 

 however, that the difficulty would not probably be so great as 

 might be expected. In Ireland the currency was changed 

 without difficulty, and in like manner the measures of capacity ; 

 and so, I conceive, would any important change, the advantage 

 of which would soon make itself felt. 



Throwing aside, as incapable of being made good (though 

 undoubtedly it might be rendered less bad), our present con- 

 fused and inconvenient system, let us consider what are the 

 essential qualities of a good and philosophical s.ystera to be in- 

 troduced in its room. And it strikes me that the following 

 particulars embrice all that can be desired:— 



1. It should have its basis in nature, and that basis should 

 be of such a kind as not to be limited to one nation or tribe of 

 thehuman family, but common to all mankind. 9. From the basis 

 the other portions should be deduced by a simple and intelli- 

 gible process, so that all should have a mutual relation, con- 

 nection, and dependence ; and these portions should embrace 

 measures of length, of superficial area, of solid capacity, and 

 of weight. 3. In each of these departments the multiplies 

 and sub-multiplies of the primary unit should proceed deci- 

 mally ; that is, the larger divisions should increase upwards by 

 tens, and the smaller decrease downwards by tenths. This 

 would put an end to all such rules as compound addition, com- 

 pound subtraction, multiplicatiou, reduction, and fractious. 

 Every arithmetical calculation would be performed by the rules 

 applicable to whole numbers; and, in fact, one-half of tho 

 processes which now iuvolve long and troublesome computa- 

 tions would be solved by inspection merely, without the use 

 of pencil or pen. And 4 — which, indeed, is implied iu the 

 three preceding conditions, it should, if possible, be such that 

 we may expect, sooner or later, the adoption of the same sys- 

 tem by all civilized nations. 



Now, a moment's consideration will satisfy us that the first 

 thing to be determined is the unit of length, for from it the 

 meas<ires of surfaces, of capacity, and of weight, can easily be 

 deduced. And according to the first of the conditions above 

 stated, we must look for a unit that has its basis in nature, 

 and is not peculiar to one locality or to one tribe of mankind. 

 Various standards of this sort have been suggested. In the 

 year 1679, Locke suggested the third part of a pendulum 

 Tibratiug seconds, as the unit of linear measure : but pendu- 

 lums require to be made of different lengths to vibrate seconds 

 at different points on the earth's surface ; and it is a matter of 

 great difficulty to determine the eiact length of the second's 

 pendulum either at the equator or any particular latitude. 

 Although this proposal has been before the world for nearly 

 two hundred years, no one pendulum has ever yet been men- 

 tioned as beating time with such accuracy that it would be 

 right to adopt it as a standard of length. A similar objiction 

 applies to another suggestion, which is, that we should era- 

 ploy, as the origin of our linear system, the space through 

 which a heavy body falls in vacuo, in a second of time. It is 

 evident that this suggestion involves all the difficulties con- 

 nected with the pendulam, and some others besides. It is 

 difficult to procure a perfect vacuum ; it is not easy to deter- 

 mine the apace described by the falling body, by observation 

 merely; the space is known approximately by calculations 

 founded on the length of the pendulum itself ; and here, still 



more thari in the ca3e of the pendulum, the varying force of 

 gravity at ditfereut latitudes would give units of varying length 

 at different points. The only proposal that remains for dis- 

 cussion, and which it is needful to consider, is that 

 for takinj,' as the unit of linear measure some de- 

 finite portion of the dimensions of the earth itself. It is 

 confessedly difficult to make any exact measurement 

 of the earth itself, or of any required portion of its surface, but 

 the thing can be done with a very close approximation to cor- 

 rectness ; and when this has been accomplished with as great 

 accuracy as can be attained, the sub-division of any one of the 

 great magnitudes thus reached will give a unit of length as . 

 accurate as can reasonably be desired. I am sure I speak iu 

 the presence of many who are well aware that there is no such 

 thing as a perfectly exact measurement of any one object in 

 the universe. All that we can do is to reduce the amount of 

 error within the narrowest possible limits, and this is most 

 easily effected by the sub-division of the dimensions of a very 

 large body, which has itself beeu measured with the utmost 

 possible correctness. Now, the c.irth itself is the largest body 

 that we can touch ; the magnitudes and distances of the heavenly 

 bodies, though iu many cases much larger than the earth, are 

 determined primarily from the dimensions of our planet. Ac- 

 cordingly it has been proposed to deduce cur standaid of 

 length either from the dinjensionsof the earth's polar diameter, 

 or from the extent of its surface, measured or computed from 

 pole to pole, in a direct line. The latter is assuredly prefer- 

 able, because from it the diameter of the earth is calculated, 

 and iu such cases it is better to employ the original than the 

 derivative magnitude. The French Government deserves the 

 credit of having first put this suggestion into practice. An 

 arc of the meridian extending from Dunkirk, iu France, to 

 the sea-shore, near Catalonia, in Spain, was measured with 

 the utmost care by Messieurs Michain and Delambre ; and 

 from this, combined with the measurements of Maupertiusand 

 Condamine, previously extended with a view to determine the 

 shape of the earth (its sphericity, as it is called), was deduced 

 the length of an arc extending from the north pole to the 

 equator. Tne 1-1 0,000,000th part of this arc was denonomi- 

 nated the mt'^tre ; a bar of platinum was constructed represent- 

 ing this length as accurately as possible ; and this bar — or 

 others directly or indirectly copied from it — is the standard 

 unit of length throughout France, and in many other countries 

 which have herein followed her example. It is equal to 39 7- 

 50 inches of our English measure, and is about { of an inch 

 longer than a pendulum vibrating seconds at the level of the 

 sea in London. Themrtre is divided decimally downwards into 

 decimetres, centimetres, and millimetres ; and multiplied deci- 

 mally upwards into decametres, hectometres, kilometres, and 

 myriametres ; the latter being, as is implied by its name, 

 equal to 10,000 metres of the scale. The specimens before 

 you show the manner iu which the metre and its sub-divisions 

 can be adapted to the purposes of drapers, carpenters, architects, 

 and so forth. A portion of a metrical surveyor's chain is shown 

 in the diagram. I ca« never survey these specimens without 

 being struck by the peculiar beauty, if I may so term it, of 

 the decimal division. 



A square formed upon a line of ten metres in length, is the 

 unit of superficial or land measure; and a cubit which has a 

 decimetre (or 1-lOth of a metre) for its measuring line, is called 

 a litre — the unit of capacity. Each of these is increased or 

 diminished by multiples or 8ul)-multlple8 of ten ; buf, for the 

 convenience of those who prefer halves and quarters to tenths, 

 each may be, and often is, divided in this manner, though all 

 arithmetical calculations are performed decimally. For the 

 unit of weight a kilogramme is used, which is the weight of a 



