January 14, 1892] 



NATURE 



255 



heated metal undergoing compression and elongation is 

 such as to insure good practical results. 



It also follows that if the heat between these points 

 can be ascertained, it may only be necessary to ascertain 

 the fusion-point of any given steel, from which the work- 

 ing temperature can be determined, for the welding heat 

 will obviously be a constant of temperature below the 

 fusion-point of the steel sample, and it is probable that 

 the discrepancies so often observable are simply due to 

 deviations from the critical temperature required for 

 welding and rolling purposes. 



The welding or rolling heat should correspond to the 

 fusion-point of steel, which is governed mainly by the 

 amount of carbon it may contain, and possibly other 

 elements may play a part in affecting the final result. 



Finally, as the results of purely practical experience, 

 the writer has been led to think that the term impurity, 

 as applied to the mixed foreign elements present in iron, 

 "is simply a conventional one, applicable only under 

 certain rigid conditions of temperature combined with 

 manipulation " ; and these must be present in fixed 

 quantities, bearing uniformly the same ratio to each 

 other. It follows that under other conditions of tempera- 

 ture and manipulation a product possessing the same 

 physical properties might be produced from a material 

 sensibly differing in composition from that quoted above. 



It is well known that those solely engaged in the manu- 

 facture of iron and steel have, "independent of the 

 teachings of science," long ago come to the conclusion 

 that iron undergoes unaccountable changes. It is asserted 

 that ordinary chemical analyses afford no explanation of 

 the observed phenomena ; further research is insisted 

 upon. To use their own words, they ask " What is iron ? 

 In our.practice something often happens to iron of which 

 your analyses afford no explanation." It is to be hoped 

 that recent research has partly solved the problem ; and 

 that, by a further study of the metal itself, some clue may 

 be found indicating more clearly than at present that iron 

 is either a true chemical compound, or, if not, subject to 

 allotropic modifications. 



Practically, it does not seem to matter which, as, to 

 quote the words of Dr. Gore, " every substance becomes 

 a more or less different substance at every different 

 temperature" {Phil. Mag., May 1890). 



John Parry. 



THE GROWTH OF THE PILCHARD OR 

 SARDINE. 



T T was long since proved that the pilchard of the south- 

 ■■■ west coasts of England and the south coast of Ireland 

 is the same species of fish as the sardine of the Atlantic 

 coasts of France and Portugal, and of the Mediterranean. 

 But there are apparent differences in the sizes and habits 

 of these fish in different regions, of which the explanation 

 has only recently been sought. The life-history of the 

 species has been studied during the past few years with 

 great care by several naturalists at various points of the 

 coasts along which its habitat extends ; and as a result of 

 these researches, the extent to which its local peculiarities 

 are real or only apparent is gradually being ascertained. 

 Thus Marion at Marseilles has established the facts that 

 the Mediterranean sardine in that neighbourhood spawns 

 chiefly in February and March, but that the spawning 

 period extends from December to May, that the adult 

 fish does not exceed 18 cm. in length, and that the 

 smallest sexually mature individuals are 15 cm. long. 

 The majority of the pilchards caught by drift-nets on the 

 south coasts of Devon and Cornwall are from 20 to 25 cm. 

 in length, while those which I have seen in the ripe con- 

 dition were 23 to 25 cm. Thus it is clear that the Medi- 

 terranean sardine, at any rate in the Gulf of Lions, is in 

 its adult state a much smaller fish than the Cornish 



NO. 1 1 59, VOL. 45] 



pilchard, although no structural differences have yet been 

 described which would separate the two as local races or 

 varieties. 



The well-known French sardine, such as we see it 

 preserved in oil in tins, is also a small fish. The sardine 

 fishery and the sardine-preserving industry in France are 

 carried on along the south coast of Brittany from La 

 Rochelle to Brest. The great majority of the sardines 

 caught there are fish from 13 to 16 cm. in length. Con- 

 sidering the short distance between Cornwall and Brittany, 

 it might be suspected that these fish are not full grown ; 

 and Prof. Pouchet, Director of the Zoological Laboratory 

 at Concarneau, tells us in his Reports that these sardines 

 are young fish which have not yet reached sexual matu- 

 rity. In fact, full-grown sardines of the same size as 

 typical Cornish pilchards are also caught on the Breton 

 coast, and are locally distinguished as " sardines de 

 dc'tive" the small fish used for tinning being called " sar- 

 dines de rogue." The adult sardines are captured princi- 

 pally in winter, the sardines de rogue in summer. The 

 question therefore arises whether small pilchards of the 

 same size as the sardines de rogue of the French coast 

 occur on the coasts of Cornwall, and if not, why not. 

 During the four years I have been at the Plymouth 

 Laboratory I have never heard of any such fish being 

 i caught by the fishermen. Not long ago I asked Mr. 

 Dunn, who has been engaged in the Cornish pilchard 

 trade the greater part of his life, if he had ever seen any 

 pilchards of the same size as French sardines, and he said 

 he never had He is connected with the factory at 

 Mevagissey, where adult pilchards are prepared in oil in 

 tins in the same way as French sardines, and he told me 

 that some years ago the owners of the factory took steps 

 to ascertain whether pilchards of small size could be 

 captured near Mevagissey. A seine of the kind used by 

 the French fishermen was procured from France, and 

 several trials were made with it ; but instead of half-grown 

 pilchards of the required size, it captured only very young 

 specimens 2 or 3 inches long. The recent capture, there- 

 fore, in nets belonging to the Marine Biological Associa- 

 tion, of young pilchards similar in size to the French 

 sardines de rogue is a matter of some interest and im- 

 portance. The discovery also adds considerably to our 

 knowledge of the growth and history of the pilchard. 



Some months ago the Director of the Plymouth 

 Laboratory was instructed to procure a fleet of small- 

 meshed drift-nets for the purpose of catching anchovies, 

 in order to ascertain at what seasons and positions and in 

 what abundance these fish appeared off Plymouth. These 

 nets are five in number, each being 60 fathoms in length ; 

 the mesh is about \ inch square, or 70 meshes to the yard. 

 They were shot a few miles outside Plymouth Breakwater 

 on November 3, 4, 5, and 6, and on each occasion the 

 chief part of the catch consisted of pilchards measuring 

 13 to 16-5 cm. in length. The rest of the catch consisted 

 of a few full-grown pilchards, a few young mackerel, a few 

 sprats, and sometimes a few anchovies. On each occasion 

 there was a considerable difference in size between the 

 smallest of the large pilchards and the largest of the 

 small. The spawning period of the pilchard off Plymouth 

 extends from the beginning of June to the beginning of 

 November— five months— and may possibly be prolonged 

 a little beyond these limits. Now all the available evi- 

 dence tends to show that even the smallest of the young 

 pilchards above mentioned, 13 cm. in length, could not 

 have reached that size if hatched the same year, even if they 

 were derived from eggs shed in May. For in the latter 

 case they would be only a little more than five months 

 old. Meyer found that herrings at five months were only 

 6 to 7 cm. long, and Marion states that the sardine at 

 Marseilles is 7 cm. long at the same age. It might be 

 argued that the Atlantic pilchard grows faster than the 

 Mediterranean sardine, but it can scarcely grow so much 

 faster as to reach 13 cm. in five months. It is pretty 



