.S7A- \\-ll.I.IAM SIEMENS, l-.R.S. I 17 



First. That of linear measurement, the measurement of area 

 within a plane, and of plane angles; comprising Geometry, Trigo- 

 imiM'-try, Surveying, and the construction of linear measures, dis- 

 tance meters, sextants and planimeters, of which a great variety 

 will be found within this building. 



The subject of linear measurement will, I am happy to state, be 

 brought before you by one whose name will ever be remembered 

 as the introducer into applied mechanics of the absolute plane, 

 and of accurate measure, 1 mean Sir Joseph Whitworth. It is to 

 be regretted, I consider, that Sir Joseph Whitworth adopted as 

 the unit of measure, the decimalized inch, instead of employing 

 the centimetre, and I hope that he will see reason to adapt his 

 admirable system of gauges, also to metrical measure, which, not- 

 withstanding any objections that could be raised against it on 

 theoretical grounds that, namely, of not representing accurately 

 the ten millionth part of the distance from one of the earth's poles 

 to its equator is, nevertheless, the only measure that has been 

 thoroughly decimalized, and which establishes a simple relation- 

 ship between measures of length, of area, and of capacity. It 

 possesses, moreover, the great practical advantage of having been 

 adopted by nearly all the civilised nations of Europe, and by 

 scientific workers throughout the world. Sir Joseph Whitworth's 

 gauges, based upon the decimalized inch, are calculated to main- 

 tain their position for many years, owing to the intrinsic 

 mechanical perfection which they represent, but the boon con- 

 ferred by their author would be still greater than it is if, by 

 adopting the metre, he would remove the last and only serious 

 impediment in the way of the unification of linear measurement 

 throughout the world. A discussion will probably arise regarding 

 the relative merits of measurement ct, bout, of which Sir Joseph 

 Whitworth is the representative, and of measurement d trait, 

 which is the older method, but is still maintained by the Standard 

 Commissioners, both in this country and in France. 



The second group includes the measure of volume or the cubical 

 contents of solids, liquids, and gases, comprising stereometric 

 methods of measurement, the standard measures for liquids, and 

 the apparatus for measuring liquid and gaseous bodies flowing 

 through pipes, such as gas meters, water meters, spirit meters, of 

 which, likewise a great variety of ancient and modern date will 



