448 



NATURE 



{March 8, 1888 



electric current, is exercising the minds of electricians just now. 

 Mr. Bosanquet has put it very clearly that when there is any op- 

 position to a physical change of such a nature that it is the greater 

 the greater the measure of the cause, and the less the measure of 

 the effect, it is clearly a resistance ; and in this sense the quotient 

 of magneto-motive force (ampere-turns among practical men) by 

 magnetic flux per unit area (magnetic induction) is clearly re- 

 sistance. It must, however, not be forgotten, that magnetic 

 permeability is the analogue of electrostatic capacity, and if we 

 regard iron as the analogue of a dielectric or an insulator, the 

 use of the term is wrong. 



The following relative figures of the cost of the production of 

 1000 watt-hours, the unit of electrical energy introduced by the 

 Board of Trade, are given by Peukert in \.\\.z Centralblatl fur 

 Electrotechnic. 



s. d. 

 Thermo-electric battery (gas) ... ... 33 4 



Bunsen battery ... .. ... ... 32 



Daniell ,, ... ... ... ... 2 2.\ 



Dynamo (gas) ... .. ... ... 06^ 



,, (steam) ... ... o 2\ 



Mengarini is continuing the work originated by Blaserna, 

 by which the maturing of wine is considerably expedited by the 

 passage of powerful currents through it, 



Heim (Hanover) has recently made some interesting measure- 

 ments of the intensity of light emitted by various artificial sources 

 of light in daily use : — 



Lamps. Candle-power. Consumption per 



•^ Candle per Hour. 



Ordinary petroleum 15 ... 3-65 grammes 



Argand (gas) 21-9 ... lO'g litres 



Welsbach (gas) ., 14-4 ... 6'6 ,, 



Wenham (gas) 28*4 ... 877 ,, 



Flat burner (gas) i6'9 ... I4"8 ,, 



Pieper arc, 6 mm 377 ... "405 watts 



Pilsen arc, lomm 1 120 ... "291 ,, 



Siemens arc, 14 mm 3830 ... '236 ,, 



Siemens glow 16 ... 3*25 ,, 



Von Lamg has measured the counter-electromotive force of 



an arc lamp, using 5 mm. carbons, and finds it 37 volts, or for 

 Edlund's formula — 



E ^ a -f- blZ, 



where a and b are constants, / the length of the arc, and C the 

 current — 



« =35 '07. t> ~ 1*32, / = 2-5 mm., C = 5 amperes. 

 He has found these constants for various other materials. Cross 

 and Shepherd (Boston) had found this back electromotive force 

 to be 39 volts. What is this so-called counter-electromotive 

 force ? Surely it is an abuse of terms. 



Mr. Shelford Bidvvell (Royal Society, March i) is con- 

 tinuing his admirable researches on the changes produced by 

 magnetism in the lineal dimensions of the different magnetic 

 metals. He finds that iron, which first expands with the mag- 

 netizing force, soon reaches a maximum point, whence it retracts 

 until it attains its original length ; but, on sti'l further increasing 

 the magnetizing force, it contracts until it apparently reaches a 

 minimum point, beyond which his means have not enabled him 

 to proceed. Bismuth appears to continually expand ; nickel to 

 continually contract ; whilst cobalt contracts, reaches a mini- 

 mum point, and then expands, approaching its original length. 

 Manganese steel was unaffected. His apparatus was so perfect 

 and sensitive that he could read a variation of one hundred- 

 thousandth of a millimetre. 



Profs. Ayrton and Perry have satisfactorily disposed of 

 the question as to whether there is any difference in the light 

 emitted by a glow-lamp when incandesced by alternate or direct 

 currents. They find no difference. The same power {3 '39 

 watts) applied gives the same light (one candle) in each case. 



THE PRESIDENTS ANNUAL ADDRESS TO 

 THE ROYAL MICROSCOPICAL SOCIETY} 



TD ETROSPECT may involve regret, but can scarcely involve 

 anxiety. To one who fully appreciates the actual, and 

 above all the potential, importance of this Society in its bear- 

 ing upon the general progress of scientific research in every field 



' Delivered by the Rev. Dr. Dallinger, F.R.S.. at the annual meeting of 

 the Royal Microscopical Society, February 8, 1888. 



of physical inquiry, the responsibilities of President will not be 

 lightly, whilst they may certainly be proudly, undertaken. 



I think it may be now fairly taken for granted that, as this 

 Society has, from the outset, promoted and pointed to the higher 

 scientific perfection of the microscope, so now, more than ever, 

 it is its special function to place this in the forefront as its raison 

 d'itre. The microscope has been long enough in the hands of 

 amateur and expert alike to establish itself as an instrument 

 having an application to every actual and conceivable depart- 

 inent of human research : and whilst in the earlier days of this 

 Society it was possible for a zealous Fellow to have seen, and 

 been more or less familiar with, all the applications to which it 

 then had been put, it is different to-day. Specialists in the 

 most diverse areas of research are assiduously applying the in- 

 strument to their various subjects, and with results that, if we 

 would estimate aright, we must survey with instructed vision the 

 whole ground which advancing science covers. 



From this it is manifest that this Society cannot hope to enfold, 

 or at least to organically bind to itself, men whose objects of 

 research are so diverse. 



But these are all none the less linked by one inseverable bond ; 

 it is the microscope : and whilst, amidst the inconceivable 

 diversity of its applications, it remains manifest that this Society 

 has for its primary object the constant progre-s of the instrument — 

 whether in its mechanical construction or its optical appliances ; 

 whether the improvements shall bear upon the use of high powers 

 or low powers ; whether it shall be improvement that shall apply 

 to its commercial employment, its easier professional application, 

 or its most exalted ."scientific use ; so long as this shall be the 

 undoubted aim of the Royal Microscopical Society, its existence 

 may well be the pride of Englishmen, and will c ;mmend itself 

 more and more to men of all countries. 



This, and this only, can lift such a Society out of what 

 T believe has ceased to be its danger, that of forgetting that 

 in proportion as the optical principles of the microscope are 

 understood, and the theory of microscopical vision is made plain, 

 the value of the instrument over every region to which it can be 

 applied, and in all the varied hands that use it, is increased 

 without definable limit. It is therefore by such means that the 

 true interests of science are promoted. 



It is one of the most admirable features of this Society that it 

 has become cosmopolitan in its character in relation to the in- 

 strument, and all the ever-improving methods of research em- 

 ployed with it. From meeting to meeting it is not one country, 

 or one continent even, that is represented on our tables. Nay, 

 more, not only are we made familiar with improvements brought 

 from every civilized part of the world, referring alike to the micro- 

 scope itself and every instrument devised by specialists for its 

 employment in every department of research ; but also, by the 

 admirable persistence of Mr. Crisp and Mr. Jno. Mayall, Jun., 

 we are familiarized with every discovery of the old forms of the 

 instrument wherever found or originally employed. 



The value all of this cannot be over-estimated, for it will, even 

 where prejudices as to our judgment may exist, gradually make it 

 more and more clear that this Society exists to promote and 

 acknowledge improvements in everyconstituent of the micro- 

 scope, come from whatever source they may ; and, in connection 

 with this, to promote by demonstrations, exhibitions, and mono- 

 graphs the finest applications of the fin-st instruments for their 

 respective purposes. 



To give all this its highest value, of course, the theoretical side 

 of our instrument must occupy the attention of the most accom- 

 plished experts. We may not despair that our somewhat too 

 practical past in this respect may right itself in our own country ; 

 but meantime the splendid work of German students and experts 

 is placed by the wise editors of our Journal within the reach 

 of all. 



I know of no higher hope for this important Society than that 

 it may continue in ever-increasing strength to promote, criticise, 

 and welcome from every quarter of the world whatever will 

 improve the microscope in itself and in any of its applications, 

 from the most simple to the most complex and important in 

 which its employment is possible. 



There are two points of some practical interest to which I 

 desire for a few moments to call your attention. The former 

 has reference to the group of organisms to which I have for so 

 many years directed your attention, viz. the " Monads," which 

 throughout I have called "putrefactive organisms." 



There can be no longer any doubt that the destructive process 

 of putrefaction is essentially a process of fermentation. 



