704 



NA TURE 



[November io, 1923 



most intercstitiK forniN is Holbe maia »p. nov., which 

 is the sniiillrst known mantis and attainn a length of 

 only 8 rnni. Mr. Tindaic mentions that it came freely 

 to fight in a camp, and was so active that it was very 

 difTicidt to capture ; it often seize<l flies and other 

 insects which nad been likewise attracted. Another 

 new mantid, J*arhierodula niajuscula, is probably the 

 largest Australian member of the family, and the 

 female measures 95 mm. long, while the outspread 

 tcgmina have an expanse of 1 13 mm. A third spiecies, 

 Orthudern ministralts I'"ab., seems to occur in all parts 

 of the continent as well as in Tasmania. It exhibits 

 a wide range of variation, which has resulted in an ex- 

 tensive synonymy ; notwithstanding its wirie distribu- 

 tion, it does not appear to have developed any clearly 

 defined local races, unless the Tasmanian form is to 

 be regarded as coming under that category. 



The Early Proboscideans. — Much has been 

 written on the genus Moentherium, which is known 

 from its remains in the Qasr-el-Sagha beds of the 

 Fayum in Egypt, and was first described by C. W. 

 Andrews of the British Museum. H. Ma'tsumoto 

 (Bull. Amer. Museum Nat. Hist., vol. 48, p. 97, 1923) 

 now reviews the species, with the aid of specimens 

 in the American Museum of Natural History, and 

 concludes that M. Schlasser was not justified in 

 regarding the smaller forms styled AI. gracile and 

 M. trigodon as sexual varieties respectively of M. 

 lyonsi and his species M. andrewsi. Schlasser retained 

 only the last two names ; Matsumoto points out 

 that, even in that case, the name trigodon has priority 

 over Schlasser 's andrewsi. He concludes, however, 

 that all four species are distinct, and he thus keeps 

 the happily named M. andrewsi on the list. He 

 regards some early Moeritherium as ancestral to 

 Palaeomastodon, with which three of the known 

 species are associated in the Oligocene (or " Upper 

 Eocene ") beds. M. gracile is known only from the 

 lower series, the Qasr-el-Sagha beds, here styled 

 Middle Eocene. , The author supports the views of 

 Andrews, and emphasises the proboscidean characters 

 as against those that have been held by others to 

 be sirenian. He remarks that, while Moeritherium 

 no doubt haunted watery places, its anatomy does 

 not indicate that it was more aquatic than Hippo- 

 potamus. 



Geology of the Weald. — The Geological Survey 

 of Great Britain has issued a memoir on " The Con- 

 cealed Mesozoic Rocks in Kent," by G. W. Lamplugh, 

 F. L. Kitchin, and J. Pringle (E. Stanford, Ltd., 

 1923 ; price 7s. 6rf.). A great deal of interesting 

 information is here brought together as to the floor 

 on which the best-studied Cretaceous rocks in Britain 

 rest, and special attention is directed to the com- 

 parison now possible of the Kimmeridge Clay of Kent 

 with that of Dorsetshire. In the Proceedings and 

 Transactions of the Croydon Natural History and 

 Scientific Society, vol. 9, pt. 3 (Croydon : Roffey and 

 Clark; price 5s., 1923), Mr. C. C. Fagg, president for 

 1922, treats of the recession of the chalk escarpment 

 in the district south of Croydon, and shows how the 

 dry gaps have been influenced bv the lowering of the 

 surface of the Gault. He points out that the River 

 Mole just below Dorking tends to disappear in summer, 

 and how, in no long geological time, it will cease to 

 run through the gap, and will be captured by tribu- 

 taries of the Wey. Numerous sections illustrate 

 this paper. It is followed by one by Mr. G. T. 

 McKay on meanders, dealing specially with the Mole. 

 The influence of the veteran geologist, Mr. Wm. 

 Whitaker, at Croydon has clearlv been fruitful in 

 guiding geological research. 



NO. 2819, VOL. I 12] 



Chemical Porcelain. — ^An article by Dr. G, 

 White on "The Manuf.-irtiin. ».f Rn<.iivi. < i.-.,«, 

 Porcelain " appears in t 

 The basis of all pottery : 

 plex, but relatively unstable, substance, f 

 poses at about 600" C, the prwliicts of 

 tion being alumina and silica. I 

 unite only at very high tempcrat 

 the use of lower temperatures yields a po.- 

 which is useless for chemical ware. Flux« 

 {e.g. silica and felspar mixture), so that a vitrih' 

 product results, though for chemical ware il. 

 amount added must be a minimum. The article : 

 illustrated with photomicrographs, and types • 

 fracture — mechanical and heat — are discussed. 



Definitions of Photometric Quantities ' ■ 

 National Illumination Committee of Great ! 

 has now supplemented the useful work it »'"^ 

 done in connexion with definitions of the > 

 metric quantities by a list of svinlw 

 luminous flux (F), candle power (J).'i: 

 and brightness (B). Greek letters ar 

 to indicate reflection, absorption, and t 

 ratios. The aim has been twofold : (a) to 

 ing practice, and (6) to avoid possible confuaion wu.. 

 international electrical symbols. Explanations .' 

 the reasons leading to the adoption of these s\ 

 are given in tabular form. Those for luminoi: 

 illumination, and brightness are already wiU--.\ 

 adopted. The only notable departure is in th ■ 

 adoption of " J " for candle power — a symbol general 

 in Germany, but not elsewhere. The reason for 

 rejecting " I," which is at present very gc- — "-- 

 used, is that this symbol is unfortunately .•. 

 assigned to current in international electrical n 

 clature. 



Corrosion of Condenser Tubes. — ^Some of the 

 more important recent results of the investigations 

 conducted for the Corrosion Committee of the In- 

 stitute of Metals are contained in a paper presented to 

 the North-east Coast Institution of Engineers and 

 Shipbuilders on October 19 by Dr. Bengough, Mr. R. 

 May, and Miss Pirret. Very rapid corrosion of con- 

 denser tubes is essentially a recent trouble, and takes 

 the form of smoothly water- worn depressions, extend- 

 ing over several feet of the tube, and mostly in certain 

 positions. Electrolytic protection fails to prevent it. 

 Should a tube survive the first few weeks under the 

 given conditions, attack of this kind is not likely to 

 occur later. The effects are not due to uneven com- 

 position of the tubes or to surface imperfections, and 

 laboratory experiments show that the cause is the 

 presence of entangled air in the water, which in 

 modern practice travels with a high velocity. The 

 critical period in the life of a tube is its early life, 

 before a coating of scale has had an opportunity of 

 forming ; once this scale has firmly established itself 

 the resistance to corrosion is very greatly increased. 

 Different waters also differ in regard to their p>ower of 

 foaming, those which readily foam being the most 

 corrosive in presence of air. The attack is usually 

 limited to certain parts of the condenser, and when 

 defects are discovered the renewal of tubes should be 

 limited to those parts, as the wholesale re-tubing of 

 the condenser may mean the removal of a large 

 number of perfectly good tubes which have already 

 received their protective coating of scale. High 

 water speeds and high vacua are the modem condi- 

 tions that have brought about this trouble. It is 

 suggested that the artificial production of a scale 

 on the tubes before putting into use may be found 

 to be practicable. 



