May 12, 1904] 



NA TURE 



Behaviour of Radium Brorr.ide Heated to High 

 Temperatures on Platinum. 



It may be of interest tn record that radium bromide 

 I'litained from Schuchardt, of Gbrlitz, and stated to be 

 pine, melts at 728° C. This number is arrived at by 

 lil.-ervations on minute specks of the substance heated upon 

 ihr platinum ribbon of the meldometer. 



At higher temperatures — up to 1600° — there is every 

 .ipjiearance of decomposition, a quiescent glass finally re- 

 maining on the hot platinum. After the experiment it is 

 found that the platinum is deeply pitted, and that in some 

 of the pits the limpid glassy substance remains imbedded. 

 Ibis glass is insoluble in hot or cold water or in HCl even 



I'M' prolonged inuuersion in the ho.t acid. It can be re- 

 ved only partially from the platinum by scraping. Its 

 ractive inde.\ is low. 



I he pitting would most readily be accounted for by sup- 

 ping a platinum bronude formed, but what, then, becomes 



I he radium? Is an :illov formed? The ribbon is found 

 111 be still radio-active after the experiment, but feebly so. 

 I have not made quantitative observations for possible 

 riMOvery of activity. J. JoLV. 



Trinity College, Dublin, May 7. 



Electromotive Force between Two Phases of the 

 Same Metal. 



I-'rom the microscopic studv of the changes which take 

 place in metals in hardening and annealing, I had been 

 liil to the conclusion that metals may occur in two phases. 

 .1 hard or amorphous phase and a plastic or crystalline 

 phase {Proc. Roy. Soc, vol. Ixxii. pp. 218, 232). In seek- 

 ing for independent evidence of this, it occurred to me to 

 try if there existed a measurable electromotive force between 

 the two phases, and I have now obtained definite proofs 

 that this is the case in all the metals which have been 

 ti-ted. In the case of silver, a thermo-junction consisting 

 of a hardened and an annealed wire gave an E.M.F. of 

 12S micro-volts at a temperature of 250° C. This tempera- 

 ture appears to be near the transition point, and beyond 

 this the E.M.F. falls to zero, as the wires are then both 

 in the same phase. Further experiments on the subject are 

 in progress, and the results will be published in due course. 



George Beilisv. 



II University Gardens, Glasgow, May 7. 



A Simt>Ie Method of Showing Vortex Motion. 



If a little aqueous fluorescein be placed in a glass tube 

 drawn out to a capillary bore, and supported vertically over 

 a tall cylinder of water, so that the orifice is just beneath 

 the surface, the fluorescein will descend through the water 

 in a fine stream. 



If the water be quite tranquil and free from any rotatory 

 motion, this stream will continue straight, unbroken, and 

 clearly defined to the bottom of the jar. 



Let a tap be given to the stand supporting the tube ; a 

 slight swelling will appear on the issuing stream and 

 gradually increase in size, widening as it goes, while the 

 part immediately behind it becomes more and more slender, 

 and finally parts altogether. 



The separated portion continues to widen,' and the velocity 

 of the centre being greater than that of the edge, it acquires 

 a motion of rotation, and becomes a perfect vortex ring. If 

 a succession of taps be given to the stand, a series of such 

 rings are formed in regular order. .As their velocities 

 diminish, their cross sections increase ; they alternately pass 

 through one another, and their motion can be observed with 

 great ease on account of the slowness with which it takes 

 place. I do not know if this method of producing vortices 

 is new or not, but at all events it possesses the merit of 

 simplicity. P. E. Bel.i\s. 



Royal College of Science, Dublin, May 3. 



Napier's Logarithms. 



Sti'DENTS interested in this subject may be recommended 

 to consult "The Construction of the Wonderful Canon of 

 Logarithms," by John Napier, Baron of Merchiston ; 

 translated from Latin into English, with notes and a 

 catalogue of the various editions of Napier's works, by 

 William Rae Macdonald, F.F.-A. (William Blackwood and 

 Sons, Edinburgh and London, iSS.i.) G. B. .M. 



NO. 1802, VOL. 70] 



THE EXCAVATOR'S VADE MECUM.' 



IF any man living is qualified to write a book on the 

 subject of excavating it is Prof. Petrie, than whom 

 no one has had a longer and wider experience or more 

 consistent success. And, as a perusal of these pages 

 will show, the work of e.xcavation is something more 

 than the mere overturning of earth with the spade 

 and extraction of such treasures as may be concealed 

 beneath it. There is not only the organisation and 

 direction of labour, with all the knowledge of human 

 — and especially of the Oriental — nature that it in- 

 volves, the adaptation to physical conditions, the com- 

 prehension of the history and' geography of the counti-y, 

 and, last but not least, the unerring eye for the dis- 

 position of cemeteries or temple sites which is almost 

 an instinct rather than a matter of experience. The 

 ideal excavator must, in addition, be a skilful draughts- 

 man and photographer ; he must have some knowledge 

 of chemistry, "geology, mechanics, and surveying, 

 besides— ce/a va sans' dire— ihe archaological know- 

 ledge which enables him to identify, estimate, and 

 classify on the spot the results of his researches. 



That the writer of this book fulfils perfectly in his 

 own person all these requirements, he would probably 

 be the first to deny ; but his long experience has given 

 him a title to speak, as it were, ex cathedra on all such 

 subjects, and though the work deals almost exclusively 

 with excavation from an Egyptian point of view, it 

 will henceforth be indispensable for its practical value 

 to all investigators in any part of the world. In fact, 

 it contains so much practical advice on every possible 

 head that one mav fancy the would-be follower of Prot. 

 Petrie somewhat 'staggered at the task set before him. 

 The apparatus laid down as essential for preservation 

 and packing of objects alone would seem to necessitate 

 the transport of a whole Whiteley's or Gamage's to 

 the Egyptian deserts. We have been sufficiently 

 curious to compile a list of materials named in these 

 two chapters. Thev include barrels, zinc trays, 

 brushes of various kin'ds, paraffin wax, tapioca water, 

 emery paper, gelatine, benzol, silicate solution, 

 glyce'rine, nitric acid, fuller's earth, sheets of glass, 

 plaster, ammonia, h3-drochloric acid and other 

 chemicals, in addition to tools and other more obvious 

 necessities. But perhaps the author regarded this list 

 as a counsel of perfection, as he gives a much shorter 

 one on pp. 112-1 1 5. 



Seriously, however, all such hints are extremely 

 valuable, and provide for every contingency and every 

 difficulty that may arise in the course of an excavation. 

 The only valid objection that might be taken to them 

 is that much of what is said is perfectly obvious to 

 a person of average intelligence, and that plenty of 

 good work on these lines has been done elsewhere 

 besides in Egypt. However, Prof. Petrie takes his 

 subject seriously and with genuine enthusiasm, and his 

 system affords a welcome contrast to that of the ex- 

 cavator for mere pleasure or for unblushingly com- 

 mercial ends, to whom archaeological results are 

 nothing, and whose labours therefore confer no benefit 

 on any save himself. If we may venture on a word 

 of criticism in general, we may say that he is inclined 

 to be somewhat too severe 'on the work done by 

 museums and bv the stay-at-home archaeologist. The 

 explorer, as M'r. Hogarth well pointed out in his 

 charming "Wandering Scholar," can never supply 

 the place of the scholar; happy is he who combines 

 both capacities in his own person, as it has been given 

 to few to do ; but the one will always be complementary 

 to the other. Hence we think Prof. Petrie top much 

 inclined to regard excavation (even with all its con- 



1 "Methods and Aims in Archasology," By W. M. Flinders Petrie 

 Pp. xviii4.2o8 ; with 66 illustrations. (London : Macmillan and Co., Lid 

 New York : The Macmillan Co.. 19:4-) Price 6j. 



