August 9, 1883] 



NATURE 



34 j 



facile prineeps in M. Lecoq de Boisbaudran's spectrum of the 

 negativs pole, and was therefore termed a by him, though to 

 the confounding of his series of Greek letters in the positive 

 pole's spectrum — I wrote of it in 1880 as "grand line peculiar 

 to cyanogen," "the powerful violet line (viz. the above) at 59,405 

 W.N.B. inch, may become useful as a reference for place to 

 many observers," and "grandly strong violet line, followed by 

 a band ; specially characteristic of cyanogen." 



But a better view of the testimony of the whole case will 

 be found in the above pair of tables, in the first of which 

 I have collected, in a rude way of my own, all the lines 

 and bands which are supernumerary in M. Lecoq de Boisbau- 

 dran's negative, as compared with his positive, pole ; and in the 

 second I have entered my former conclusions from gas-vacuum 

 tube observations of what spectral lines and bands are peculiar 

 to the compound gas cyanogen. C. Piazzi SMYTH 



15, Royal Terrace, Edinburgh, July 25 



The Earliest Known Plotting Scale 



The Babylonian statues recently acquired for the Louvre by 

 the mission of M. de Sarzec are of great interest in the history 

 of measurement. The earliest datable measuring rods hitherto 

 known are two Egyptian masons' cubits of wood, of the reign of 

 Hor-em-heb in the fifteenth century B.C. ; but on these statues 

 we find represented not merely a mason's rod, but a finely- 

 divided plotting scale, and the date of the e figures is placed 

 before the fifteenth century B.C. Of course the accurate lengths 

 of cubits can easily be recovered from the dimensions of build- 

 ings of the earliest periods ; but no measures, or accurate repre- 

 sentations of such, are preserved to us from the primitive times. 



There are several of these diorite statues of King Goudea in 

 the Louvre, some rather less and some rather more than life size ; 

 all finely executed in a style superior to anything of the later 

 times from Mesopotamia, with which we were already familiar. 

 They are wrought by means of tubular drills and graving tool 5 , 

 by which lengthy and delicate inscriptions are cut all over the 

 surfaces ; the tools employed seem to have been very similar to 

 those used by the early Egyptians for their statuary in diorite, 

 which I recently described at the Anthropological Institute. 



The statues which now concern us are two seated figures of an 

 architect (or perhaps the king, as founder) ; these each bear on 

 the knees a drawing board, 6"3 x 11/3 and 7*4 x 12*7 inches 

 respectively. One board is plain, the other has an elaborate 

 outline of a fortified town, showing all the buttresses and turns 

 of the wall. By the right hand of each figure lies a drawing 

 stylus, and along the front of each board a plotting scale, sub- 

 divided along both outer and inner face. 



These scales have a sloping face along each side, like modern 

 scales, but meeting in a ridge at the top, like French plotting 

 scales, without a level space. The breadth is '90, and height 

 •33 inch, sloping therefore ab:ut 36° ; the length is just over 

 ioj inches, or half a cubit, the terminals being lines, with a 

 small surplus beyond them. 



The subdivisions vary on the different sides ; but the general 

 arrangement is a uniform series of spaces, which we will call 

 digits ; these are each rV of the half cubit, or '653 inch. Then 

 along one side of each rod the alternate digits are subdivided ; 

 thus there can be no confusion between digit lines and sub- 

 divisions. The dividing lines run the whole width of the face ; 

 they are about -fa inch wide, and scored out nearly as deep into 

 the diorite. The subdivisions are of halves, thirds, fourths, 

 fifths, and sixths of a digit ; and two sixths are carried over to 

 the other side of the scale, and there further divided into 

 twelfths and eighteenths of a digit ; this last fraction being only 

 ^5 of an inch. 



By calculating a normal scale from the various digit lines (as 

 described in "Inductive Metrology," p. 31) the average error 

 of division may then be computed. It is about the same for 

 the digits and also the subdivisions, varying on different sides 

 from -009 to '013 inch ; the mean error of all the digit marks is 

 •01 1 inch, or about half the breadth of a cut. But it is not to 

 be expected that mere decorative representations like these would 

 be divided with the same care as actual working scales. The 

 mean value of the cubit deduced from these scales is 20'89±'07 

 inch, which is apparently a long variant of the old 20-63 cubit, 

 and not the later Assyrian cubit of 21/4 or 2i - 6. 



The actual values of the division; of the two sides of each 

 scale are as follows, stating the amounts as differences from the 

 normal scale in thousandths of an inch, which enables the varia- 



tions to be most plainly seen. The points measured were about 

 one-third from the bottom edge toward the top ridge. 



The plain dots show that there was no mark ; the dots in 

 brackets where a mark is defaced, or the whole surface destroyed. 

 The great error of 058 inch is due to a cut run askew, the line 

 being as accurate as the others on the outer face of the rod. 



I am indebted to M. Ledrain for kindly granting me permis- 

 sion to take the measurements from these statues. 



Bromley, Kent W. M. Flinders Petrie 



A Result of our Testimonial System 



A little incident has come under my notice of such a cha- 

 racter that I think it ought to be made known to the readers of 

 Nature. 



A candidate, whom I will call Mr. A. B., for a vacant scien- 

 tific chair in this country writes to an eminent German professor 

 for a "testimonial," and in his letter there occurs the following 

 remarkable sentence : — 



". . . 17 7>.fy, 83 



"Dear Sir, — I intend applying for the vacant chair of . . . 

 at . . ., and would feel grateful if you could send me a testi- 

 monial saying a few favourable things of my contributions to the 

 science of . . . 



"... I hope that you will not think me too bold in asking 

 this request, and as I know your time is too valuable to be tres- 

 passed on by a stranger, I beg that you will accept the inclosed." 



The German professor, whom I will call Prof. C, thereupon 

 writes to a di>tinguished English professor, who is a personal 

 friend of his, the following letter, which has been placed in my 

 hands with the request that I will add a few comments. The 

 letter, which I give in its original language in order that none of 

 its force may be lost, runs as follows : — 



