December 23, 19 15] 



NATURE 



465 



I 



at Saltash, Cornwall, in February, 1913, the other 

 at Busum, in Schleswig-Holstein in August, 1913. 



That closely similar and nearly related species may 

 sometimes be more easily distinguishable by their be- 

 haviour than by their physical characteristics is shown 

 by Mr. Walter Ritchie in the Scottish Naturalist for 

 December, wherein he describes "The Smaller Pine 

 Beetle (Myelophilus minor) in Aberdeenshire." M. 

 minor and M. piniperda are two small bark-beetles, 

 which are to be distinguished one from another only 

 after very careful scrutiny. Yet the tunnels which 

 they drive beneath the bark of trees are strikingly 

 different in character, so that there can be no possible 

 confusion in the plan of the mother and brood-galleries 

 of the two species. The mother-gallery of M. pini- 

 perda forms a vertical shaft from which the very long 

 larval galleries are given off on either side at right 

 angles. In M. minor the mother-gallery is biradiate, 

 and runs transversely to the long axis of the tree- 

 trunk, while the larval-galleries are very short, and 

 running at right angles to the mother-gallery. They 

 thus come in consequence to run in the same direction 

 as the mother-gallery of M. piniperda. 



Parts 10 (Series A and B) of the third volume of 

 the Review of Applied Entomology have just been issued 

 by our Imperial Bureau. Of special interest among 

 the summaries of foreign literature are accounts of 

 Prof. N. A. Cholodkovsky's latest work on the 

 Chermesidae (Dept. Agri., Petrograd, 19 15), and if 

 Dr. O. N. Paleitchuk's detailed instructions for the 

 treatment of bees infected with Nosema apis. Unfor- 

 tunately we are not told if the prescription, when 

 adopted, proved effectual. 



The Consular Report (Annual Series, No. 5496, 

 19 15) on San Thom^ and Principe indicates the remark- 

 able success achieved by the Portuguese authorities 

 in their drastic measures taken to exterminate the 

 tsetse-fly and sleeping sickness on these islands. The 

 death-rate has fallen steadily, and in 1914 only 52 

 people died of the disease at Principe ; only eight per- 

 sons on the island were still suffering from it, and 

 they were all old cases. The conquest of the epidemic 

 has no doubt been due to the campaign against the 

 tsetse-fly. None have been caught since April 11, 

 1914, although the reward has been raised from one 

 to five dollars per fly. Thirty-four flies were caught in 

 1914. The report remarks: — "Apparently there is 

 every reason to believe the fly has now been completely 

 exterminated in the island." 



The Records of the Indian Museum, vol. xi., part 4, 

 contains some valuable notes on Indian parasites of 

 fish by Mr. T. Southwell. He is of opinion that some 

 species at least of the larval Trematodes which live 

 in the skin and flesh of fishes may mature in the 

 human intestine. The ectoparasitic crustacean, 

 Argulus foliaceus, he found to be a serious menace 

 in confined tanks. This was demonstrated in the case 

 of a number of Indian carp {Labeo rohita), which, 

 about a month after being placed in the tank, became 

 NO. 2408, VOL. 96] 



sluggish and floated on the top of the water. When 

 removed they were found covered with Argulus. All 

 the fish were then captured, scraped clean, and re- 

 turned to the water. An upright bamboo was then 

 placed in the centre of the tank, and this was imme- 

 diately used by the fish as a mean of rubbing off their 

 unwelcome adherents. No more deaths occurred after 

 this date. It is unlikely that frogs assisted in keep- 

 ing down this parasite, though the author inclines to 

 this view. 



According to the theory of parallel axes, any quad- 

 ratic function of the co-ordinates and their rates of 

 change of a system of masses may be represented as 

 the sum of two terms, one being the same as if the 

 whole mass were concentrated at the centre of mass, 

 and the other representing the corresponding function 

 of the relative co-ordinates and their rates of change 

 I referred to the centre of mass as moving origin. Un- 

 fortunately, however, there has been a tendency in 

 certain quarters to reproduce misstatements in which 

 similar properties are alleged to hold good with regard 

 to points other than the centre of gravity. Prof. E. 

 Bidwell Wilson communicates to the American 

 Mathematical Monthly, vol. xxii.. No. 6, a note on 

 " Linear Momentum, Angular Momentum, and Kinetic 

 Energy," in which it is sought to enunciate the precise 

 forms which these dynamical magnitudes assume when 

 expressed in terms of the motion of an arbitrary point 

 and of the relative motion of the system with respect 

 to that, point. It is desirable that these results should 

 be studied in detail by teachers of mechanics, but it 

 will be evident from a perusal of the paper that the 

 student should be warned invariably to choose the 

 centre of mass as the moving point with respect to 

 which the dynamical magnitudes under consideration 

 are expressed as the sum of two terms. We have 

 seen it stated that in forming equations of motion it 

 is only possible to take moments about either a fixed 

 point, the centre of gravity, or the instantaneous centre 

 in the case of small oscillations. As a matter of 

 fact, moments may be taken about any point what- 

 ever provided that the mass accelerations of the system 

 are properly specified in the form of a force through 

 the centre of gravity and a couple. 



The Journal of the Washington Academy of Sciences 

 for November 19 contains an abstract of a paper on 

 the mechanical properties of zinc-bronze by Mr. H. S. 

 Rawdon, of the Bureau of Standards, which will ulti- 

 mately appear in full in the Bulletin of the Bureau. 

 The alloy has the composition, copper 88, tin 10, and 

 zinc 2 per cent., and considerable variation in the 

 method of preparation may be made without the struc- 

 ture being seriously affected. In the cast condition it 

 consists of a matrix of relatively large crystals of a 

 solid solution of tin and possibly zinc in copper, in 

 which are embedded numerous particles of a hard, 

 brittle eutectoid. When broken in tension the fracture 

 occurs along the cleavage planes of these crystals, and 

 their size and relative positions in the cross section of 

 a test bar have a considerable effect on its strength. 

 The most serious cause of fracture is, however, the 



