Terry Simpson in USMA 23351 wrote:
Joseph B. Reid wrote:See para. "4.2 Other non-SI units" in the metric bible. It advises "their use is not encouraged". It points out that there are three centimetre-gram-second systems of units in the field of electricity and magnetism, viz. the CGS Electrostatic System, the CGS Electromagneic System and the CGS Gaussian System.Yes. It does mention previous metric systems. This can be read as consistent with currently valid parallel metric systems (as many people here think). Or it can be read as consistent with historical context to a singular metric system that invalidates all those that went before (as I think and the NIST apparently thinks). One of my big criticisms of the SI brochure is that it embeds SI guidelines in historical story telling. This makes it very difficult for the reader to extract current validity from previous validity that is now invalid.
I think that any intelligent reader of the SI brochure would have no difficulty in distinguishing SI from metric units that are now obsolete. These units are listed in Tables 9 and 10. If they were not included in the brochure, how could the reader interpret historic documents that use them?
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
