SCIENCE- GOSSIP. 



339' 



derived from these fundamentals and are called 

 derivative units. 



From what has now been said, it will be seen 

 that calculations based upon metric dimensions 

 and measiires are more readily performed than 

 with our English units. There are no troublesome 

 5^ and 30:^ measures to contend with. The units 

 of the various tables are moreover connected with 

 the unit of length by a simple relation. 

 Force and Work. 



It will, perhaps, be interesting to glance at two 

 other quantities on the metric system — derivative 

 units, and to compare them with those obtained 

 upon our system. These are force and work, and 

 they are tabulated as follows : — 



the difficulty of making the change has been enor- 

 mously exaggerated. He thinks that in a fort- 

 night people wovild become so much accustomed 

 to the perfect simplicity and easy working under 

 the metric system that they would feel that,, 

 instead of its being a labour to pass from the on^ 

 system to the other, it woidd be less than no 

 labour. That is to say, it would be a very great 

 saving of labour after the first day or two of begin- 

 ning to use the new system. 



The Decimal Association is doing good work 

 in helping on the change. Its inflvience is increas- 

 ing and its list of supporters include the names of 

 some of the foremost men in science, politics and 

 commerce. The President of the Board of Trade 



Quantity. 



Unit on Metric 

 System. 



Unit on English 

 System. 



Definition on Metric 

 System. 



Definition on English 

 System. 



Force. 



Dyne. 



Poundal. 



1 

 The force that, acting The force, that acting 

 upon a mass of 1 upon a mass of 1 

 gramme for 1 second, pound for 1 second, 

 gives it a velocity of gives it a velocity of 

 1 cm. per second. 1 foot per second. 



Work. 



Erg. 



Foot-Poundal. 



The work done by 

 one dyne in acting 

 through 1 cm. 



The work done by 

 1 poundal acting- 

 through 1 foot. 



Gramme- 

 centimetre. 



Foot-Pound. 



The work done in 

 raising one gramme 

 through 1 cm. 



The work done in rais- 

 ing 1 pound throiigh 

 1 foot. 



It will be seen that two units of work are given 

 in each system. The gramme-centimetre and the 

 foot-pound are the units more generally used in 

 engineering and are calculated upon the weight cif 

 a body and not upon its mass. The gramme-centi- 

 metre is, as a matter of fact, found too small for 

 practical purposes and the kilogramme-metre is 

 used instead. A kilogramme-metre is the work 

 done in raising one kilogramme throiigh a height 

 of one metre. 



Use of Metric System. 



From a consideration of the foi^egoing tables and 

 definitions and of the simplicity of the metric sys- 

 tem, it is not surprising that other nations have 

 adopted it. Between twenty and thirty coun- 

 tries have taken it up either as a compulsory 

 measure or as a permissive one. The niimeroixs 

 reports that have been sent in by different consuls 

 from variovis parts of the world point out how 

 much our foreign trade is suffering through our 

 not using the decimal system. In those countries 

 where it is in force, intending purchasers fail to 

 vmderstand quotations based upon our present 

 weights, measures and coinage. 



The change will certainly be a momentous one 

 for English people and there mtist be confusion 

 jxist at first. Lord Kelvin, however, believes that 



received a deputation of representatives from the 

 Decimal Association, and other bodies, on 

 March 22nd svippoi-ting the compulsory use of the 

 system in this country. 



Suffolk House, Dartmouth Parle Hill, London, N, W. 



WATKIN'S MOUNTAIN ANEKOID. 



IN oiir notice of this beautiful instrument in 

 last month's issue of Science-Gossip (p. 294), 

 an unfortunate prin- 

 ter's mistake crept 

 into the account of 

 the fractional devia- 

 tion or error. This 

 was made to repre- 

 sent To oVo o' whereas 

 it should have been 

 equivalent to a loss 

 of 0-00225 or xoWoo 

 of an inch. This 

 latter fraction is 

 remarkable, and 

 doubtless most of 

 our readers must 

 have noticed the 

 improbability of the 

 former statement. 

 We have now plea- 

 sure in giving a figure of Colonel Watkin's aneroid 

 barometer. 



