126 



NA TURE 



[June 8, 1882 



delicate to detect differences in the force of gravity in conse- 

 quence of our being lifted farther from the centre of the earth 

 every time by the terrain tide as it passed between our feet, could 

 be established in conjunction with the experiments on earth- 

 tremors. John Milne 

 Imperial College of Engineering, Tokio, Japan 



Limulus 



Concerning the systematic place of Limulus, I should like 

 to draw attention to a habit which has, as far as I know, never 

 been alluded to in discussions, viz. the manner of casting its 

 skin, mentioned by me in Deformation of Insects {Mem. Compar. 

 Zoology}. Limulus splits the skin exactly around the front margin 

 of the head. Among Crustacea the Decapods at least split the 

 skin around the hind margin of the carapace. Insects split the 

 skin in the longitudinal middle line of the occiput and thorax, 

 with the later addition of a transversal split on the head. I 

 have seen cast skins of Scorpio, Pseudoscorpions, Hydrachna, 

 and Arachnids, but they are not now at band for a sure verifi- 

 cation. As far as I remember all of them split the skin in the 

 middle line of the anterior parts. At least I do not remember 

 to have seen any transversal anterior split. H. A. Hagen 



Cambridge, Mass. 



The Utilisation of Ants in Horticulture 



Dr. C. J. Macgowan has sent me from Han Chow, Province 

 of Hain'n, China, a little paper on the " Utilisation of Ants as 

 Insect Destroyers in China." It seems that in many parts of 

 the province of Canton the orange trees are injured by certain 

 worms, and to rid themselves from these pests, the inhabitants 

 import ants from the neighbouring hills. The hill-people 

 throughout the summer and winter find the nests of two species 

 of ant-, red and yellow, suspended from the branches of various 

 trees. The "orange ant breeders" are provided with pig or 

 goat bladders baited inside with lard. The orifices of these they 

 apply to the entrance of the bag-like nests, when the ants enter 

 the bladders, and, as Dr. Macgowan expresses it, "become a 

 marketable commodity at the orangeries." The trees are 

 colonised by placing the ants on their upper nranches, and 

 bamboo rods are stretched between the different trees, so as to 

 give the ants easy access to the whole orchard. This remedy has 

 been in constant use at least since 1640, and probably dates from 

 a much earlier peri id. This is certainly a new way of utilising 

 ants, which as a rule are deservedly considered a nuisance by 

 the horticulturist. I should like to learn from any entomological 

 reader of Nature whether the facts communicated have before 

 been known in Europe, and, if so, whether the species of ant 

 has been determined. C. V. Riley 



Washington, D.C. 



Aurora Australis 



Atril 17. — Evening very dark ; air close and sultry; ther- 

 mometer at 65. About 6.35 p.m. noticed a broad sheath of dull 

 osy red in the south, stretching upwards towards the zenith ; from 

 outh-east to south was spread a bright greenish-yellow glare, 

 ufficiently luminous to enable us to read the figures of a lady's 

 sSmall watch. Shortly afterwards, the sky from east-by-south to 

 south-southwest was illumined with a ruddy glow deepening to 

 dark red ; at the mo>t easterly point nf the auroral light were 

 broad pulsiting streamers of great brilliancy ; these extended to 

 south-east-by-east. Could not detect the slightest sound from 

 aurora. Weather continued fine. April 20. — This evening 

 there was a wide-spread glare of aurora] light, with greater 

 range, but of far le-s brilliancy than marked the grand display 

 on the 17th. Weather fine and clear. T. H. Potts 



Ohinitaki, N.Z., April 21 



"Cuprous Chloride Cell" 

 As the account given of my cuprous chloride cell in your 

 report (NATURE, vol. xxvi. p. 96) of the Proceedings of the 

 Royal Society of Edinburgh i> rather misleading, I hope I may 

 be excused if I make a fe.v remarks on the subject. It is there 

 stated that my cells suffered greatly froai lo,s. This is not a 

 correct sta e nent. There are two ways 111 which the work 

 expended i 1 charging a secondiry battery is k>;.t. When a 

 secondary battery is being charged, the L.M.F. between the 

 terminals of the battery is higher "than the normal E.M.F. of the 



battery with open terminals, work being expended in heating 

 the cells. When the charged cells are used to supply a current, 

 the E.M.F. between the terminals is lower than the normal 

 E.M.F. with open terminals, work being again spent in beating 

 the cells. This source of loss is unavoidable, and is in practice 

 very serious. I need only refer to the recent experiments in 

 Paris with Faure accumulators, which were, I think, reported in 

 Nature. The second source of loss is the local action in the 

 cell. This depends upon the chemistry of the cell. I have 

 found the estimation of loss from this cause a difficult matter, but 

 I think I am justified in saying that the loss from this cause in 

 my cell is very small, when it is properly constructed. In fact, 

 when used as a primary, its advantage is that it does not suffer 

 from diffusion and consequent local action as all double-fluid 

 cells do. I think it deserves a trial as a primary battery on this 

 account. It is necessary to protect the cuprous chloride from 

 air, covering it with water being quite sufficient. If this is done 

 it should be a very durable form of cell A. P. Laurie 



King's College, Cambridge 



[The statement that the cells suffered greatly from loss is in 

 our report coupled with an additional statement which implies 

 that other secondary cells have the same fault ; so that Mr. 

 Laurie is in no worse predicament than other inventors of 

 secondary batteries. Unless Mr. Laurie's cell is in this respect 

 superior to others, the report can hardly be regarded as mis- 

 leading. — Ed.] 



Physico-chemical Lecture Experiments 



A very striking lecture experiment, which I have never seen 

 performed or described, and which illustrates the reaction, by 

 double elective affinity, of dry solids, is the trituration together 

 in a mortar of corrosive sublimate and iodide of potassium. The 

 result is a brilliant scarlet coloration of iodide of mercury. If 

 a large crystal of the one is rubbed on a crystal of the other, a 

 scarlet precipitate (if the word may be so applied) is formed at 

 every point of contact. From the brilliancy of the colour the 

 experiment may be readily seen by a large number of spectators. 



June 5 Leigh Clifford 



CUPS AND CIRCLES 



AN important addition to the literature of " Cups and 

 Circles" and Cup-marked Stones, 1 has just been 

 issued as part of the fifth volume of " Contributions to 

 North American Ethnology," printed by the Department 

 of the Interior in their series of the publications of the 

 U.S. Geographical and Geological Survey of the Rocky 

 Mountain Region. The literature of the subject as 

 regards the Old World is already extensive, and the 

 object of Mr. Rau's work is to collect and systematise 

 the existing information regarding the " cup and ring 

 cuttings " that have been observed on rocks and boulders 

 in Europe and India, and to add to this systematised 

 knowledge an account of those that are now known in 

 America. 



The first monograph on these archaic forms of sculp- 

 turings on rocks and stones was that of A. E. Hohnberg, 

 on the Lapidary Sculpturings of Scandinavia (" Skandi- 

 navien's Hallristningar," Stockholm, 1848), but though 

 copiously illustrated, it remained in a great measure a 

 sealed book, from its being written in Swedish ; and it 

 was not till the publication of Mr. Tate's memoir on 

 "The Ancient British Sculptured Rocks of Northumber- 

 land and the Eastern Border" (Alnwick, 1S65) ; the ex- 

 haustive essay on the same subject by the late Prof. Sir 

 James Y. Simpson, entitled "Archaic Sculpturings of 

 Cups, Circles, &c, upon Stones and Rocks in Scotland, 

 England, and other Countries" (Edinburgh, 1867); and 

 the larger work, prepared under the direction of f he late 

 Algernon Duke of Northumberland, entitled " Incised 

 Markings on Stone found in the County of Northumber- 

 land, Argyle, and other Places, from Drawings made in 

 the Years'1863 and 1864" (London, 1869) that the atten- 

 tion of archaeologists generally was awakened to the 



1 " Observalions on Cup-shaped and other Lapidarian Sculptu 

 Old World, and in America." By Charles Rau. (Washington, 18 



