446 



NATURE 



[April 6, 1876 



early English ctira, cetera, or more modem cittern. 

 " Fu la cetera usata prima tra gli Inglesi," says Galilei 

 Examples of instruments of this kind are frequent, but 

 M. Engel startles us by exhibiting the following as an 

 original " Gennan Fiddle, IXth century, St. Blasius." 



Fig. 7.— Fiddle String. Xlllth Century. (St. Blaise.) 



The above is copied from Gerbert's " De Cantu et 

 Musica Ecclesiae," vol. ii., and is derived from a manu- 

 script which was formerly in the monastery of St. Blaise, 

 and which Gerbert describes as "about 500 years old ! " (ex 

 cod. San. Bias, annorum. circ. 500, p. 139) as he wrote in 

 1774. That would bring the date to the second half of the 

 thirteenth century, instead of the eighth or ninth, as M. 

 Engel states in his text. Moreover the plate is not in- 

 tended to exhibit a fiddle, but a fiddle-j/;-/«;o-. It is called 

 lyra, and the word is explained in two of the glossaries 

 collected by Mr. T. Wright. A fiddle would have had more 

 strings than one, in the thirteenth century, and the strings 

 would have been fastened to pegs instead of a single 

 string passed through a ring. 



It will be seen from the above that the claims for 

 G vmany are put forth in the strongest hght by M. Engel, 

 av.d that otV.cr countries may not so readily acquiesce in 

 them. We ourselves should raise many demurrers to his 

 claims and conclusions, but they would apply to the pre- 

 fatory essay and to the musical instruments of Europe, 

 rather than to those of the rest of the world. While we 

 cannot but wish that M. Engel's nationality had been 

 less strongly developed, he is justly entitled to the credit 

 of having ably fulfilled his commission, and of having 

 exerted extensive research. 



OUR BOOK SHELF 



Notes on the Practical Chemistry of the Non-Metallic 

 Eleme?tts and their Compouftds. By William Procter, 

 M.D., F.C.S., Lecturer on Chemistry at St. Peter's 

 School, York. (London : Simpkin, Marshall, and 

 Co. York : the Northern Educational Trading Co.) 

 This is a handbook on the Practical Chemistry of the 

 Non-metallic Elements, designed to meet the require- 

 ments of pupils of Mechanics' Institutions, and of Science 



Classes of a similar kind. The true man of science wel- 

 comes every worthy means of spreading scientific truth, 

 and docs everything in his power to propagate that truth. 

 He will regard with a jealous eye each work brought 

 forward with a view of extending a knowledge of the 

 sciences ; and with a work intended for the use of a class 

 whose opportunities of gaining knowledge are very 

 limited, his scrutiny will be all the closer. A book written 

 for the information of such should be couched in the 

 simplest language, and the sense conveyed should be at 

 once clear and comprehensive. In these respects Dr. 

 Procter's little work cannot be termed a success. To use 

 no stronger expression his language is frequently very 

 vague. For example, on page 14 the author in speaking 

 of " Chemical Affinity " says : " hence, in order that this 

 force may be exercised by the particles coming within 

 the sphere of each others' attraction, the substances must 

 be in the state of liquid or gas." There can be but one 

 way of understanding the latter part of this quotation, 

 viz., that no chemical action can take place, unless the 

 materials taking part in that action are each and all of 

 them in a liquid or gaseous state. Dr. Procter is scarcely 

 less happy in his definitions of bases, acids, &c. He 

 says : " An acid is a compound of .an electro-negative 

 radical with hydrogen, which hydrogen it can ex- 

 change for a metal or basylous radical, and it is there- 

 fore replacable." Again, " A salt is a compound pro- 

 duced by the action of a base upon an acid with the 

 displacement of the hydrogen of the latter." How 

 can such definitions convey to the minds of pupils 

 proper ideas of the true natures of acids and bases ? Such 

 explanations would not inappropriately be termed indefi- 

 nitions. Chapters are devoted to chemical calculations, 

 and chemical manipulations, and here doubtless the 

 readers will find many useful hints for their guidance in 

 the preparation of their apparatus, &c. In the body of the 

 book Dr. Procter treats of the non-metallic elements, 

 giving the ordinary methods of preparing them, and their 

 compounds, and illustrating the characteristics of each 

 by interesting and instructive experiments. A few pages 

 devoted to the chemistry of water, qualitative analysis of 

 gases, and the preparation of ordinary reagents, complete 

 a book, which, designed for a good purpose, and contain- 

 ing much useful information, at the same time shows want 

 of care in compilation, and also^ lacks lucidity. Printer's 

 errors are much too numerous. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neithtr can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications.^ 



The Use of the Words " Weight " and " Mass " 



Nothing could illustrate more forcibly the necessity of render- 

 ing definite the meaning of some of our present fundamental 

 terms in connection with the science of dynamics, than a com- 

 parison of my letter to you on this subject (vol. xiii. p. 325) 

 with the letter of Mr. Stoney, in reply to it (vol. xiii. p. 385), 

 and that of Mr. Walker who follows Mr. Stoney. 



When we who call ourselves teachers do not agree as to the 

 signification of the most elementary terms we use, it is not to be 

 wondered at, if those who come to learn should fail to attain 

 clear ideas on a part of the science, where such confusion of 

 nomenclature prevails. 



My letter to you was for the purpose of pointing out an ambi- 

 guity of language, and of suggesting, in order to get rid of 

 this ambiguity, not an alteration of the meaning of any word 

 whatever, but a very simple restriction in the use of words, and 

 the bringing into more frequent employment a very valuable 

 old word — gravity — which has been lying ready for use but left 

 almost idle. Mr. Stoney admits the ambiguity to be a very 

 real one. 



Mr. Stoney, however, says : "I fear Mr. Bottomley's remedy, 



