698 



NATURE 



[February 26, 1920 



the contortions which produce " figure ") are easily 

 discerned. The denser heart wood is differentiated 

 from the sap wood, the summer and spring 

 growths of the annual rings are readily identified, 

 and defects such as knots or grub-holes show up 

 with astonishing clearness. Kaye and Knox 

 showed some radiographs of aircraft timber and 

 timber-structures taken during the war on behalf 



Fig. 4.— Radiograph of aeroplane hollow "box " strut, showing badly fitting 

 internal end-block split by screws. (Kaye and Knox.) 



of the Aeronautical Inspection Department (Fig. 4). 

 The method is particularly useful in the case of 

 hollow or laminated components, which cannot 

 otherwise be thoroughly inspected except by 

 destructive tests. Bad gluing, shoddy workman- 

 ship, and a variety of timber blemishes are detect- 

 able with ease, even on the fluorescent screen. 



Fig. 



5, — Golf balls, showing absence of core in " floater^ " and irregular 

 core in others, (hunic Research Laboratories.) 



There appears to be considerable scope for this 

 branch of radiography. 



The radiographing of minerals is an easy means 

 of detecting the presence of very dense elements 

 such as uranium or tungsten. Pilon showed a 

 good example of the method. The structure of 

 golf balls is a somewhat unexpected subject 

 (Batten). The "non-floaters" are wound on a 



NO. 2626, VOL. 104] 



core of heavier rubber ; some of the cores were 

 spherical, but others were not — to the probable 

 detrirrient of accuracy in long putting or driving. 

 Undoubtedly the standardised championship balls 

 of the future will have to satisfy an X-ray test ! 



A neat method of testing the electrically heated |! 

 clothing of aeroplane pilots was shown by the 

 Sunic Research Laboratories. The heating strip 

 is sewn within the lining of the leather garment, 

 and any break or kink in the element can easily 

 be " spotted " on the fluorescent screen. The same 

 laboratories showed radiographs of outer covers of 

 motor and aeroplane tyres, and a variety of welds 

 in metal tubes and plates, one of these of a steel 

 plate \ in. thick being of particular excellence 

 (Fig. 6). The Cox-Cavendish Co. showed a some- 

 what similar collection, and Chambers and Rankine 

 displayed examples of their curious "diffraction" 

 and multiple image X-ray photography. 



Among the most novel exhibits were those by 

 Heilbron illustrating the X-ray examination of old 

 paintings with the object of detecting alterations 

 or additions made since the original work. Success 

 in discovering any such falsifications -would be 



I 



Fig. 6.— Bad weld in steel plate? h in. thick. (Sunic Research Laboratories.) ; 



possible only if the paint used in the original work J 

 were denser than that used in the additions. Some J 

 of the ancient pigments used by the masters are: 

 obscure in composition, but the blacks, for ex- 

 ample, of a more modern day are largely carbon,^ 

 and very transparent. Two examples of the 

 method were shown, both by Dutch masters of 

 the early sixteenth century. In one, a panel of the 

 Madonna by St. Jans, the X-rays showed that the 

 arms (which appear in a stiff and unnatural atti- 

 tude) formerly held the Child, and in the other, 

 the "Crucifixion" by Engelbrechtsz (Fig. 7), the 

 radiograph revealed a number of "restorations," 

 including the painting of the portrait of a former 

 "donatrice" over the picture of a monk. As the 

 Times remarked in a recent leader, this method of 

 detecting the presence of later additions imposed 

 on the work of the original artists suggests a gregt 

 field for the re-investigation of palimpsests and 

 ancient manuscripts hitherto regarded as carrying 

 only their face value. Under the trivial inscrip- 

 tions of medieval monks there may be revealed 

 older matter of priceless worth. We commend 

 the notion to the directors of the various art 

 galleries and museums. 



Space considerations have compelled a some- 



