November ii, 1897] 



NATURE 



31 



HIGH PRESSURE ELECTRICITY.^ 

 ■T~*HIS book is not a mere ordinary Edition de luxe, for 

 ■*• it is probably the most sumptuous book in connec- 

 tion with electricity that has ever appeared. The life-like 

 vividness of forty-one beautifully executed photographic 

 reproductions of electric brushes and streamers make you 

 hear the banging of the battery of many " ten-gallon " 

 Leyden jars ; while the description of these illustrations, 

 from the largeness of the type used, the wide spacing of 

 the lines, the two- to three-inch margin that surrounds 

 them, and the blank page that intervenes between every 

 two pages of printed matter, induces a feeling of luxury 

 in the reader, and makes him hope that the theoretical 

 inferences will be as good as the very thick paper on 

 which they are printed. 



Lord Armstrong starts with the very striking experiment 

 which he performed with his hydro- electric machine half a 

 century ago. Two glasses of distilled water were placed 

 near together, and a thread of cotton, which was coiled 

 up in the one, had its end placed so as to dip into the 

 other glass. Then on highly electrifying the glass of 

 water in which the cotton was coiled negatively, and the 

 other glass of water positively, the thread crept out of its 

 glass into the other one, while a stream of water passed 

 in the opposite direction. 



From this he has been led to conclude that an electric 

 current consists of two streams— a negative one in the form 

 of a core flowing in one direction surrounded by a sort 

 of sleeve of positive electricity flowing in the opposite 

 direction ; and he suggests, on page 24, that instead of 

 negative and positive the names "Inward"' and "Out- 

 ward " would better meet his views. 



He cites as an illustration of his theory the formation 

 of the crater at the end of the positive carbon of an 

 electric arc, and the knob at the end 

 of the negative carbon ; both of 

 which he considers are produced by 

 the scooping out effected by the 

 " lines of force," which he considers 

 follow some such path as that indi- 

 cated on the accompanying figure 

 copied from the book. 



There are various reasons, how- 

 ever, with which Lord Armstrong is 

 apparently unacquainted, for believing 

 that the scooping-out theory is not 

 correct ; for example, when a thin 

 carbon rod is put endways inta an 

 arc the rod is simply pointed like a 

 pencil, with no appearance of any 

 directed scooping action. Whereas, 

 if Lord Armstrong's " lines of force " 

 were correct, we should expect to 

 find a cavity scooped out on one side 

 of the carbon rod near the middle 

 of the arc, and another on the other side near the edge. 

 But this only happens when the carbon rod is wide, and 

 is placed so as to split up the arc into two distinct arcs. 



Some of the illustrations are photographic reproductions 

 of dust figures obtained with brush discharges, while 

 others of them were produced by causing a violent dis- 

 charge from a large battery of Leyden jars to take place 

 from a metallic disc resting on an insulated photographic 

 plate, the disc being in some experiments positive, in 

 others negative. In other cases two photographic plates 

 were placed back to back with the sensitive sides out- 

 wards, and the positive and negative electrodes were 

 placed against the two sensitised surfaces respectively. 



The figure formed at the negative electrode was found 

 to be smaller than that produced at the other, and in 

 answer to the question " How can this be reconciled with 



1 "Electric Movement on Air and Water, with Theoretical Inferences." 

 By Lord Armstrong, C.B., F.R.S. Pp. vii H- 55, and plates. (London: 

 Smith, Elder and Co., 1897 ) 



--N^i-. 



^\ 



NO. 1463, VOL. 57] 



the assumption that negative and positive action are 

 equal ? " the author remarks on page 26 : — 



" The answer is obvious if we admit that the negative 

 represents suction, and the positive pressure, because in 

 that case the negative flow will be resisted by condensa- 

 tion, while the positive will be helped." 

 And on page 44 he suggests, as a possible hypothesis, 

 that as in a pump, 



" The negative stroke, representing suction, must take 

 the lead of the positive, and will have to draw from 

 a neutral atmosphere. In doing so it will create a deficit 

 in the environment which will aid inductively the impulsive 

 energy of the positive." 



On page 49 are described experiments in which 

 negative streams were projected from an annular elec- 

 trode upon a dust plate with a positive metallic ring 

 beneath, and the author, in reference to the dust figures 

 produced, remarks : — 



" Their general appearance is strikingly like pictures 

 of physiological cells ; and what is more strange, we 

 see them in every state of fission, from small beginnings 

 to complete separation, and in every case the divided 

 form displays the same internal structure as the original 

 form from which it springs. I have already spoken of 

 electricity as organised motion, and we have here an 

 example of it carried to the very verge of life." 



All this is probably intended only as a poetic fancy, 

 but it reads strangely in close juxtaposition with a dis- 

 cussion on matter and motion, ether and atoms. 



But, whatever may be the opinion of the theoretical 

 portion of this book, whether we consider that the inward 

 flow of negative electricity and the outward flow of 

 positive are supported by the experiments, there can be 

 no doubt that the illustrations form a series of valuable 

 records of electric discharges. W. E. A. 



THE REV. P. B. BRODIE, M.A., E.G.S. 



IN the death of the Rev. P. B. Brodie geological 

 science has lost one of its oldest cultivators, one 

 who so long ago as 1834 was elected a Fellow of the 

 Geological Society, and who was widely known for his 

 researches on the fossil insects of the Secondary form- 

 ations of England. 



Mr. Brodie, who was born in 18 15, was the son of 

 an eminent lawyer, and nephew of the distinguished 

 surgeon Sir Benjamin C. Brodie, Bart. He was 

 educated at Emmanuel College, Cambridge, and coming 

 under the influence of Sedgwick, a taste which he had 

 previously manifested for geology was developed into a 

 life-long enthusiasm for the science. 



Entering the Church in 1838, the duties of his calling 

 took him as Curate to Wylye, in V^iltshire, and for a 

 short time to Steeple Claydon, in Buckinghamshire. 

 Later on he became Rector of Down Hatherley, in 

 Gloucestershire, and finally Vicar of Rowington, in 

 Warwickshire. In all these districts he found that a 

 rich harvest of geological facts could be gathered. 



His earliest observations were on the Purbeck strata 

 of the Vale of Wardour, and he then discovered many 

 insect-remains, and also the Isopod which was named, 

 by Milne-Edwards, Archaoniscus Brodiei. Continuing 

 his researches in the Vale of Gloucester, on the Lias and 

 Lower Oolites, he soon found many unrecorded fossils, 

 and notably many remains of insects, and he thus came 

 to publish, in 1845, his well-known " History of the 

 Fossil Insects in the Secondary Rocks of England." 

 An active member, for a time, of the Cotteswold 

 Naturalists' Field Club, Mr. Brodie was later on a 

 staunch supporter of the Warwickshire Natural History 

 and Archiieological Society, and a founder of the 

 Warwickshire Naturalists' and Archaeologists' Field 

 Club. He was the life and soul of field-meetings, full 



