588 



NA TURE 



[April i8, 1895 



A PAPER which will have considerable interest for those who 

 have to design and use electrical apparatus, where wood or 

 slate is often used as the insulator, appears in the Pro- 

 cudings of the American Academy. The subject of the paper 

 is the electrical resistance of certain poor conductors, such as 

 wood and stone, and is by Mr. B. O. Peirce. The author has 

 examined a great number of samples of different kinds of woods 

 and stones under different conditions as to dryness, a most im- 

 portant point, and although, as might be expected, the individual 

 results differ somewhat widely, he considers the mean results 

 give a very fair idea of what may be expected in practice. The 

 author has also tried the effect of soaking the different materials 

 in hot melted paraffin, and finds in every case, especially if the 

 specimen has been previously well dried, that such treatment 

 not only increases the specific resistance, but by preventing the 

 absorption of moisture prevents the falling off in the reiistan ce 

 otherwise observed when such bodies as stone or wo^d are ex - 

 posed in a damp place. The following are some of the resu Its 

 for the specific resistance obtained in megohms ; the first num - 

 ber denotes in each case the lowest value observed, and .|the 

 second number the mean value -.—Mahogany 310, 610; hard 

 pine 17, 1050; white pine 360, 1470; vulcanised fibre 3, 60 ; 

 slate 184, 280 ; white marble 2000, 8S00. The samples of 

 wood were all well seasoned, and the resistance was measured 

 in the direction of the grain, the resistance across the grain 

 being generally from 20 to 50 per cent, higher. The samples 

 of stone were dried in the sun for about three weeks before 

 being tested. 



A SIMPLIFIED phonograph is described by A. Koltzow in the 

 Centralztitung fiir Oplik iind Mechanik. A conical tracing 

 point is used for recording the sound waves. This has the 

 advantage of durability, and if it should wear out on one side , 

 it need only be ;tumed round its axis. The tracing-point is 

 attached to one arm of a lever, the second and longer arm being 

 provided with a membrane. For some purposes the membrane 

 is replaced by a stretched string. The cylinders consist of a 

 very hard soap. They will stand several hundred renderings. 

 Alter use they can be turned down by 002 mm., so that one 

 cylinder will suffice for 200,000 words. 



In the Comptes rendus of the Paris Academy of Sciences of the 

 1st inst., as briefly stated in our abstract last week(p.576). Prof. 

 Mascart presented a note by the Abbe Maze, stating that in a 

 collection of astronomical documents at the National Observa- 

 tory, a register had been foimd containing thermometrical and 

 other observations made by the astronomer I. BouUiau, between 

 25 May, 1658, and 19 September, 1660. Up to the present 

 time, it was not known that observations hid been male at 

 Paris prior to those of Lahirc. These observations are of some 

 interest, being among the earliest thermometrical readings on 

 the continent, and they fill up a gap in the climatological 

 history of Paris. It is also noteworthy that the thermometer 

 used was one of the Academy del Cimento. 



A RKCENT number of Modern Medicine and Bacteriological 

 Rrji€W contains a notice of Dr. Pictet's interesting experiments 

 on the application of intense cold as a therapeutic measure. 

 According to this investigator's observations, calorific radiations 

 of a lower temperature than - 65° pass through all the ordinary 

 conductors of heat ; a fur overcoat or a wooden board offering 

 no more resistance than a pane of glass or other transparent 

 medium to the passage of a sunbeam. Dr. Pictet experimented 

 upon himself in a frigorific well, in which a temperature of 

 - 100' C. to no' C. was maintained. He was wrapped in 

 warm clothes and thick furs, and at the end of four minutes 

 he stated that he experienced intense hunger, which in- 

 crcaMd ; after eight applications of eight or ten minutes 



NO. 1329, VOL. 51] 



duration his appetite became normal, and his digestion greatly 

 improved. 



The last number of lhe£o//etino of the Italian Geographical 

 Society criticises the proposed nomenclature of some of the 

 rivers of East Africa, as given in a sketch map in the Geo- 

 graphical youmal illustrating the explorations of the American 

 traveller. Dr. Donaldson Smith. The names to which the 

 Italian Society objects are those of Dr. Smith himself and of 

 his English companion, Mr. Gillett, which have been applied 

 to the upper and middle course of the Webi Shebeli and the 

 Web respectively. We are bound to admit that the criticism 

 is well-founded, as it is contrary to authorised usage to apply 

 European names when the native names can be ascertained. 

 We have little doubt that Dr. Smith will, before the end of his 

 explorations, discover some features still unknown which may 

 fitly be called after him and perpetuate the memory of his ex- 

 cellent geographical work. 



Mr. H. Rutgers Marshall, whose work on "Pain, 

 Pleasure, and -Esthetics" was reviewed in Nature (vol. 1. p. 3), 

 contributes to the April number o( Mind An article, " Emotions 

 versus Pleasure-Pain," in further elucidation ot his views. Mr. 

 Marshall is fully alive to the importance of evolutionary de- 

 velopment, and his treatment of the emotions is therefore of 

 interest to students of comparative psychology. It is unfortu- 

 nate, however, that the term "instinct " is used in an extended 

 sense which will scarcely be acceptable to those who approach 

 the subject from the biological side. The phrases, " imitation 

 impulse," "art impulse," " benevolent impulse," would appeal 

 to them as more satisfactory than "imitation instinct," "art 

 nstinct," &c., since they have grown accustomed to the appli- 

 cation of the term instinct to the manifestation of particular 

 activities. But a consensus of opinion on psychological nomen- 

 clature seems at present impossible. .\nd in any case, Mr. 

 Marshall's views are well worthy of careful co nsideration. 



An experiment of considerable interest in connection with 

 the transmission of optical signals has been performed by 

 M. Charles Henry at the Depot des Phares. The question 

 was whether rhythm in a succession of signals increases or 

 diminishes their visibility ? This was solved by means of a 

 revolving drum, the surface of which contained sixty holes 

 illuminated by a source of light placed at the axle. The drum 

 was 3 feet across, and was driven by clockwork. By varying 

 the speed of the drum and the brightness of the light, and by 

 closing some of the holes at regular or irregular intervals, all 

 the conditions of the experiment could be varied at pleasure. 

 The chief difficulty in this, as in most physiological experi- 

 ments, lay in bringing the eye back to its original state .ifter 

 each experiment. It was sometimes found impossible, even 

 after keeping in the dark for close upon half an hour, to restore 

 the observer's eye to its original state of sensibility. But it was 

 conclusively shown that it is possible to increase the range 

 through which an optical signal will carry by arranging the 

 succession of flashes according to a sufficiently complex non- 

 rhythmical law. 



PROiiAbLY no better example of an invention borrowed or 

 adapted from nature could be found than is afforded by llie 

 sand-blast. As is well known, the invention, now a quarter o( 

 a century old, consists of a stream of sand or other abrasive 

 powder, usually dry, but sometimes mixed with water, projected 

 with more or less force and velocity to strike and pulverise the 

 surfaces of glass, stone, metal, and other materials upon which 

 it is directed. The many applications of this method of 

 abrasion were recently described by Mr. J. J. Holtiapffel, at 

 the Society of Arts. It appears that glass is almost immedi- 



