60 



NATURE 



[November i6, 1899 



concerned, it compares favourably with gutta-percha. The Elec- 

 trician is of the opinion that the material at present lacks the 

 flexibility necessary to the core of a submarine cable, and also 

 the strength and elasticity required for a golf ball. Perhaps 

 with improved methods of manufacture these qualities can be 

 given to "Velvril," but until then gutta-percha will hold its 

 own as the most suitable substance for these two purposes. 



A FEW years ago the phenomena of "Barisal Guns," and 

 other similar noises, were discussed at some length in the 

 columns of Nature. A valuable contribution has recently 

 been made to this interesting subject by Prof. A. Issel, in a 

 paper published in the Bollettino of the Italian Seismological 

 Society. The author's chief object is to describe the detonations 

 which were heard at about the time of the Umbria- Marches 

 earthquake of December i8, 1897. These detonations are quite 

 distinct from the sound which generally accompanies an earth- 

 quake-shock. They are rather crashes, more or less prolonged, 

 and resemble the boom of thunder or the report of heavy guns 

 at a distance. Sometimes they are isolated ; at other times they 

 ■occur in series, following one another at brief intervals. 

 Generally they begin with a strong blow, which has very often 

 a slightly metallic sound, and then gradually diminish in number 

 and intensity until they cease, but there may be one or more re- 

 newals of activity. To many persons the crashes seemed to come 

 from Monte Nerone, where the epicentre of the earthquake was 

 situated. They are frequently heard at other times by the in- 

 habitants of the middle Appennine region, and are known to 

 them by the name of Bombio. Very often they occur in close 

 connection with earthquakes, and they may be followed imme- 

 diately by a slight shock or tremor ; they are also stronger and 

 more numerous during epochs of maximum seismic activity. 

 Prof. Issel correlates these crashes with those known in other 

 places as Marinas, Mist-Poeffers, &c. ; and, as these phenomena 

 are especially characteristic of seismic districts, he regards them 

 for the most part as due to endogenous causes. 



Electricity is rapidly gaining ground as a motive power 

 for harbour and dock works and for traction on canals. In 

 France haulage by electricity has been in use on some of the 

 canals for several years, and, besides being found economical, 

 has been of special value for working the boats through 

 tunnels. The system is now to have a trial in this country, 

 a portion of the Leeds and Liverpool Canal near Wigan 

 being fitted for electric traction ; and it is anticipated that, 

 besides other advantages, a saving in the cost of traction of 

 50 per cent, as compared with horse haulage will be effected. 

 On the Dortmund and Ems Canal in Germany, recently 

 opened for traffic, the cranes and other machinery at the 

 terminal stations, and all the work at the locks connected with 

 the opening and closing of the gates and sluices are to be 

 operated from a central station, where electricity is to be pro- 

 vided by steam power. The haulage along the canal is to be 

 effected by a small electric locomotive running along the tow- 

 path, and obtaining its supply from trolly wires. On the Erie 

 Canal one or more systems have already been tried with partial 

 success. It is now reported that the storage battery system is 

 to be introduced ; an electric traction engine will run along the 

 tow-path and haul a canal boat filled with storage batteries of 

 sufficient capacity to furnish current for the traction engine and 

 the boats towed by it. The locks of the North Sea and Baltic 

 Canal, and also the new lock of the Amsterdam Canal at 

 Ymuiden, are both worked by electricity, which is found to have 

 great advantages over hydraulic power in winter when sharp 

 frosts prevail. In this country, at Southampton Docks and 

 other places, cranes are in use worked by electricity. 



A THESIS on "The Memory Image and its Qualitative 

 Fidelity," reprinted from the American Journal of Psychology, 

 NO. 1568, VOL. 61] 



has been received from Dr. I. Madison Bentley. The results 

 of experiments carried on for the special investigation of the 

 visual memory image and its fidelity to an original presentation 

 have led to several conclusions of psychological interest. It 

 appears that discs— grey and coloured— shown and remembered 

 in daylight, tend to grow light in the visual memory, while grey 

 discs shown in a dark chamber display a tendency in the visual 

 image to grow dark during an unilluminated interval. These 

 results indicate that the condition of the retina in respect to 

 stimulation during the memory interval is important for the 

 memory image. Illuminated and unilluminated intervals, 

 where all other conditions are constant, are followed by different 

 judgments with the same memory stimuli. It is therefore con- 

 cluded that in all experiments with brightness and colour, where 

 a time interval is involved, care should be taken to control the 

 state of the visual organ. It is not improbable that a similar 

 caution would apply to other sense memories. The results also 

 show that memory is not to be regarded as a storehouse of 

 perfectly conserved images, but that the most simple memories 

 are continually exposed to change, and that it is, at times, only 

 by the combination of various memorial resources that retention 

 is made definite and exact. 



The intermittent treatment o_ sewage in bacteria coke-beds 

 forms the subject of a second report presented to the London 

 County Council J by their chemist. Various investigations were 

 carried out and are here recorded with the object of ascertaining 

 the most effective method of constructing and working the coke- 

 beds, and the data obtained form an interesting contribution to 

 the literature, now considerable, daily accumulating on this 

 method of sewage treatment. 



The reports of the malaria expedition in Italy under the 

 direction of Prof. Koch receive adverse criticism at the hands or 

 Dr. Grassi, writmg in the Atti dei Lincei, viii. (2), 8. Among 

 the points at issue it would appear that Koch, in the reports 

 referred to, still admitted the possibility of malaria being pro- 

 pagated by CiiUx pipiens, a view long since abandoned by 

 Grassi on circumstantial evidence, which he now summarises in 

 detail. Much of the evidence which led Grassi to attribute the 

 propagation of malaria to Anopheles and not to Culex has been 

 given in previous papers in the same journal. 



The well-known experiment of the early popular text-books 

 on "freezing and boiling water simultaneously" under the 

 exhausted receiver of an air-pump being difficult to perform in 

 practice, Mr. R. W. Quick describes in the Physical Review 

 another mode of achieving a similar result. This is a continu- 

 ation of the experiment commonly described under the heading 

 "water boiled by cold," in which the tightly-corked flask 

 containing the water and steam is cooled, first with iced water, 

 and then with a mixture of solid carbon dioxide and ether, until 

 ice forms as the water boils — or the flask bursts. As Mr. Quick 

 remarks, there must not be sufficient residuum of air in the flask 

 to keep the pressure above o'46 cm. (the vapour pressure of ice 

 at 0° C), otherwise no amount of cooling would be effectual in 

 causing boiling and freezing simultaneously. 



A PAPER by Prof. Archibald Barr, on " Similar structures and 

 machines," read before the Institution of Engineers and Ship- 

 builders in Scotland, is appearing in the form of a series of 

 illustrated articles in Engineering. The disproportionality 

 between large and small structures required to ensure corre- 

 sponding strength in supporting weight is illustrated by figures 

 showing the difference in structure between the skeletons of 

 large and small animals, and also by diagrams showing the 

 Britannia and Forth Bridges reduced to the same span. 



The Proceedings of the annual meeting of the Indiana 

 Academy of Science, held at Indianapolis at the end of December 

 last, contains quite a number of mathematical papers, foremost 



