January 12, 191 1] 



NATURE 



>47 



l.uclidian plane. Unless some unforeseen fallacy in this 

 investigation should be discovered which has escaped 

 Prof. Carslaw's notice, we have here a convincing proof 

 ll that Euclid's parallel postulate is incapable of demonstra- 

 tion. In fact, it is argued that if any inconsistency existed 

 1 the Bolyai-Lobatschewsky postulate this inconsistency 

 uould be extended by Prof. Carslaw's " ideal " system to 

 Fuclidian geometry. Do not these arguments point to the 

 view that Euclid's postulate should be regarded as a 

 property of matter rather than of space? 



Ik the American Architect for November 23 Mr. Wm. H. 

 (loodvear describes measurements of 1910, undertaken on 

 behalf of the Brooklyn Museum, of the spiral stairway of 

 the Leaning Tower of Pisa. The main result of these 

 leasurcments is to confirm the author's view that the 

 iciination of the tower was intentional, and was not due 

 . subsidence after or even during construction. The main 

 vidence on this point is derived from an examination of 

 the steps between the thirteenth and sixty-ninth. Not only 

 does the mean height of the ceiling increase by i foot 

 10^ inches between the thirty-fifth and forty-ninth steps, 

 hut there is an increase in the downward dip of the ceil- 

 ig to the inner wall of about 8J inches in the whole 

 iterval. .As the stairs in question represent the extremi- 

 •5 of the line of greatest slope, the effect of these changes 

 ^ to throw the weight of the structure off the overhang- 

 ic; side. On the higher floors these variations appear to 

 nve been abandoned, presumably on the ground that the 

 ifety of the structure was sufficiently secured without 

 lem, whereas if the inclination were accidental it is 

 bvious that the tendency would be to increase the pre- 

 cautions as the subsidence increased. The author further 

 *| points out the advantages from an aesthetic point of view 

 -f the standing of the Leaning Tower in a depression or 

 well," and also of the change of inclination of the 

 upper storeys, both of which support the theory of inten- 

 ■\ tional inclination of the structure. 



The measurements of the magnetic properties of iron, 

 -teel, nickel, and cobalt at the temperature of liquid air, 

 which have been made by Dr. R. Seattle and Mr. H. 

 Gerrard, and were described in the Electrician for 

 December 23, 1910, confirm the view generally held on 

 the strength of results obtained at higher temperatures, 

 viz. that decrease of temperature increases hysteresis. 

 The curves given for the hysteresis losses as functions of 

 the magnetic induction in alternating and in rotating 

 fields are of the same general form at the temperature of 

 quid air as at ordinary temperatures. The loss in cobalt 

 in a rotating field is about twenty times that in nickel. 

 The authors make no reference to the Langevin-Weiss 

 theories, but, so far as one can judge from the curves, 

 their results do not furnish any material support for those 

 theories. 



Vol. iii. of the Journal of the Municipal School of 

 Technology, Manchester, consists of nearly four hundred 

 pages of reprints of papers communicated by the staff and 

 students to scientific societies and to the technical Press 

 during the year 1909. The principal papers deal with 

 mechanical and electrical engineering and with chemistry, 

 and show that in these subjects, at least, the Manchester 

 School stands in a position which no other technical school 

 or polytechnic in the country has approached. Of the 

 ^hirty papers, two may be selected as t3'pical of the work 



e school is doing. The first, by Prof. Nicholson, deals 



with experiments directed to the removal of the obscurity 



which enveloped the subject of the transmission of heat 



from the furnace gases to the water in a steam boiler, 



NO. 2150, VOL. 85] 



and some of the results obtained have already been in- 

 corporated in boiler design. The second, by Prof. Knecht 

 and Mr. J. P. Batey, contains the results of examinations 

 of a number of dye-stuffs in solution in order to settle the 

 question whether these substances exist in solution as 

 colloids or not. The authors conclude that the dyes tested 

 do not. These examples serve to show how successfully 

 the Manchester School of Technology is bringing the 

 power of science to bear on the industries of which Man^ 

 Chester is the centre. 



An interesting article on photo-elasticity, by Prof. E. G. 

 Coker, appears in Engineering for January 6. Account is 

 given of apparatus and experimental results obtained at 

 Finsbury Technical College, the experiments having for 

 their object the determination of the condition of stress 

 in transparent bodies by the effect which these latter, when 

 subjected to such stresses, produce on polarised light 

 passed through them. A special optical bench designed 

 bv Mr. F. Cheshire is used, in which a lantern, fitted 

 with an arc lamp, projects a beam of parallel light. The 

 beam is polarised by a Nicol's prism, then passed through 

 the specimen, which latter is stressed by some convenient 

 apparatus. A lens focuses the beam on a second Nicol's 

 prism, which serves as an analjser, and the image of 

 the specimen so formed is thrown on a screen or sensitive 

 plate. A feature of the article is the reproduction in 

 colours, by the three-colour process, of a large number 

 of photographs taken on Lumi^re plates direct from the 

 specimens under stress. These are of special interest to 

 engineers, and include examples of beams, tension 

 members, a furnace flue, circular hooks and chain links, 

 a locomotive plate spring, a square threaded screw and 

 nut, and a pillar. Examples are included showing the 

 disturbance in the stress distribution caused by notching 

 the specimens in various ways, and also the effect of a 

 non-axial load on a tension member. Probably glass is 

 the material possessing properties most closely resembling 

 materials in general use by engineers, but, owing to the 

 difficulty of preparing glass specimens, xylonite has been 

 used. 



Mrs. H. Periam Hawkins sends us a copy of a new 

 (the fourth) edition of " The Stars from Year to Year," 

 in which the account of Halley's comet, to which refer- 

 ence was made in the notice of the book in last week's 

 Nature (p. 304), is brought up to date. \Ve do not quite 

 understand why the earlier edition should have been sent 

 to us for notice when a new edition was to be issued a 

 few weeks later. 



The current quarterly issue of Mr. C. Baker's catalogue 

 of second-hand instruments for sale or hire has reached 

 us. Particulars are given of more than 1500 pieces of 

 scientific apparatus which can be bought or hired at the 

 second-hand department at 244 High Holborn, London. 

 From the same house comes a very complete list of 

 additions since 1909 to the stock of lantern-slides of 

 scientific interest. 



Mr. Edward Stanford announces for publication on 

 January 16 the third edition, rewritten and enlarged, of 

 " The Building of the British Isles," by Mr. A. J. Jukes- 

 Browne. It is eighteen years since the last edition of this 

 work was issued, and much fresh matter has consequently 

 been embodied in the new book. 



In the paragraph relating to the " Live Stock Journal 

 Almanack " in Nature of December 29, 1910, the name 

 Lord William Cecil should have been Lord .Arthur Cecil. 



