Jan. 17, 1884] 



NA TURE 



polypites, giving to the ring which they occupy on the 

 lower surface of the float, a dark yellowish tint from the 

 colour of the yellow cells, found along the rudimentary 

 proboscis of the Medusa: buds, as well as along the 

 chymiferous tubes. The large marginal tentacles are of 

 a bluish tint, their knobs of a darker colour. The 

 smaller polypites occupy on the lower surface that 

 portion of the mantle which covers the ring formed by 

 the so-called white plate of Kolliker round the base of 

 the single central polypite. Sometimes these polypites 

 are seated in cavities of the white plate, and sometimes 

 projections of this latter will be found to e.vtend far up 

 into the lower part of the small polypites. This white or 

 pinkish plate consists of an irregularly anastomosing 

 system of needles and spurs, or of bars of greater or 

 smaller size, leaving a series of narrow openings for the 

 passage of the tubules. Prof. A. Agassiz suggests the 

 alliance of Porpita with the Hydrocorallinee, basing this 

 suggestion on the presence of the white plate, and of its 

 peculiar structure, which reminds him of the porous 

 structure of the corallum of Sporadopora, Allopora, 

 Millepora, and although, of course, not having the 

 regular horizontal floors of the latter, yet possessing, 

 like these genera, large pits, the whole mass being 

 riddled with passages and openings, forming the spongy 

 mass of the white plate. If this homology be correct, it 

 shows far-reaching affinities in the Porpitidae. The Plates, 

 twelve in number, give a great number of anatomical 

 details, and there are full-sized and coloured representa- 

 tions of the two species described. 



HUGHES' NEW MAGNETIC BALANCE 



ANEW magnetic balance has been described before 

 the Royal Society by Prof D. E. Hughes, F.R.S., 

 which he has devised in the course of carrying out his 

 researches on the differences between difterent kinds of 

 iron and steel. The instrument is thus described in the 

 Proceedings pf the Royal Society : — 



" It consists of a delicate silk-fibre-suspended magnetic 

 needle, 5 cms. in length, its pointer resting near an 

 index having a single fine black line or mark for its zero, 

 the movement of the needle on the other side of zero 

 being limited to 5 mms, by means of two ivory stops 

 or projections. When the north end of the needle and 

 its index zero are north, the needle rests at its index zero, 

 but the slightest external influence, such as a piece of 

 iron I mm. in diameter 10 cms. distant, deflects the 

 needle to the right or left according to the polarity of 

 its magnetism, and with a force proportional to its power. 

 If we place on the opposite side of the needle at the same 

 distance a wire possessing similar polarity and force, the 

 two are equal, and the needle returns to zero ; and if we 

 know the magnetic value required to produce a balance 

 we know the value of both. In order to balance any wire 

 or piece of iron placed in a position east and west, a 

 magnetic compensator is used, consisting of a powerful 

 bar magnet free to revolve upon a central pivot placed at 

 a distance of 30 or more cms. so as to be able to 

 obtain delicate observations. This turns upon an index, 

 the degrees of which are marked for equal degrees of 

 magnetic action upon the needle. A coil of insulated 

 wirC; through which a feeble electric current is passing, 

 magnetises the piece of iron under observation, but, as 

 the coil itself would act upon the needle, this is balanced 

 by an equal and opposing coil on the opposite side, and 

 we are thus enabled to observe the magnetism due to the 

 iron alone. A reversing key, resistance coils, and a 

 Daniell cell are required." 



The general design of the instrument, as shown in a 

 fomewhat crude form when first exhibited, is given in the 

 figure, where A is the magnetising coil within which the 

 sample of iron or steel wire to be tested is placed, b the 

 suspended needle, C the compensating coil, and M the 



magnet used as a compensator, having a scale beneath 

 it divided into quarter degrees. 



The idea of employing a magnet as compensator in a 

 magnetic balance is not new, this disposition having been 

 used by Prof, von Feilitzsch in 1856 in his researches on 

 the magnetising influence of the current. In von 

 Feilitzsch's balance, however, the compensating magna 



was placed end-on to the needle, and its directive action 

 was diminished at will, not by turning it round on its 

 centre, but by shifting it to a greater distance along a 

 linear scale belovv it. The form now given by Hughes to 

 the balance is one of so great compactness and conveni- 

 ence that it will probably prove a most acceptable addition 

 to the resources of the physical laboratory. 



WINTER LIFE AT SPITZBERGEN 



THE following is an extract of a report by one of the 

 personnel of the Swedish Aleteorological Expedition 

 of the wintering at Spitzbergen : — 



One of the deepest fjords of Spitzbergen is the Ice 

 Fjord on the w'est coast. On a map of the islands it will 

 be seen, some fifteen miles from the mouih, to split into 

 two smaller ones. The promontory which divides the 

 two is Cape Thordsten. It is formed of slate rocks some 

 2000 feet in height, from which in some places precipices 

 descend perpendicularly into the sea, and in others 

 valleys slope down into the plain. The latter is furrowed 

 by streamlets and deep ravines, while the rocks around- 

 are the breeding places of every sea bird of the Arctic 

 fauna, as, for instance, the seagull, the auk, the rodge, and 

 the Uria grylle. In the plain reindeers graze, and on the 

 mountains ptarmigans and snow-sparrows breed. The 

 plain is covered with grass, rather strongly interspersed, 

 with moss, but here are to be found many plants and 

 flowers, such as Polynwnium puleiielluni, Dryas ortope- 

 itila, the white and red saxifrage, the Spitzbergen poppy, 

 and the common buttercup. 



In the plain close to the mountain the huts are situated 

 which now bear the name of " Smith's Observatory," from 

 the munificent equipper of the expedition. The buildings 

 were erected here some ten years ago by the Ice Fjord 

 Company, which was formed for the utilisation for guano 

 of the coprolite deposits found in the adjacent mountains. 



On July 21, 1882, the vessels of the expedition arrived 

 here, but it was at that period doubtful whether we should 

 establish our station here, as the mountains around con- 

 tain a large quantity of hyperite, a mineral which it was 

 feared would aft'ect the magnetical instruments. We 

 found on landing a line of metals up the hill, with 

 a gradient of 45°, a winch being fixed at the other end for 

 its working. Here was also, still intact, the little 

 dwelling house on four poles, alongside which we found 

 the material required for the building of a new house as 

 stated in works on Spitzbergen. Near to the house is a 

 cross raised with the following inscription : Her hviler 

 Stdvet af 15 Mand, som dode her i Foraaret 1873. Fred 

 med deres Stdv. This is the epitaph to the Norwegian 

 fishermen who sadly perished here ten years ago. 



