Correspoudence — T. G. Bonneij. 141 



the temperature is accurately recorded both iminediately before and 

 after passing the crystal, the authors have been able to prove definitely 

 that the temperature at which gypsum becomes uniaxial is for sodium 

 light 91°, for red C and greenish-blue F hydrogen light 89°, and for 

 the violet hydrogen line near G 87°. These temperatures agree 

 precisely v^ith those observed for the exact superposition of the pair 

 of images of the spectrometer slit, afforded by a 60° prism cut to give 

 the a and y3 refractive indices. Owing to the large correction, 

 necessary for conduction of the crystal holder when the ordinary Fuess 

 air-bath heating apparatus was employed, and to the difficulty in 

 determining it, former determinations of the temperature at which 

 a section-plate of gypsum becomes uniaxial were too high, and did 

 not agree with the prism observations. — Dr. G. F. H. Smith : Note on 

 a large Crystal of Anatase from the Binnental. The crystal exhibits 

 a combination of the forms a (100), t(313), and s(]13), and the others 

 not prominent, and it is remarkable for the fact that the faces t have 

 been entirely replaced by numberless tiny crystals with the forms 

 s(113), Jc {112), J) {III), and e (101), and the same orientation as the 

 large crystal. 



OOI^KiESI=03SriDEIS3"OEl. 



THE DEAWING ON A EED CEAG SHELL. 

 Sir, — I think we shall do well to be cautious in recognizing 

 a "long-lost brother" in the Red Crag, though his credentials have 

 been accepted by no less an authority than Sir E. Ray Lankester. 

 At any rate I doubt whether the carving on a shell of Pectunculus 

 glijcimeris, cited in your last number by Dr. M. C. Stopes, strengthens 

 the evidence in favour of his existence. I had the opportunity of 

 examining this a few years ago and possess a photograph, which 

 Mrs. Stopes kindly gave me at that time. The design and execution 

 of the engraving reminded me rather of a piece of grotesque, dating 

 from the nineteenth century, than of the e^fforts of Palgeolithic man, 

 as displayed on the walls of caves or in other relics of his handy work. 

 That, however, is a matter of opinion, but what weighed even more 

 with me when I examined the specimen was the state of the shell and 

 the carvings. The former, especially its hinge-teeth, showed the very 

 slight corrosion usual in Crag specimens of this Pectunculus, while the 

 surface of the carved parts was smooth and comparatively fresh- 

 looking. I do not doubt that the late Mr. Stopes was convinced that 

 he had obtained possession of a genuine relic of Red Crag Man, but, if 

 Ave could trace out the history of the specimen before it came into his 

 hands, I think we should find this another instance of an " old friend 

 with a new face ". 



T. G. Bonnet. 



STEATIGEAPHICAL NAMES. 



SiE, — It is probable that few geologists whose studies are limited 



to a single country, or even to a single continent, have any adequate 



conception of the large number of names that have been proposed 



either for geological formations or for periods of geological time. 



