i8o 



SCIENTIFIC NEWS. 



[Feb. 24, 1 5 



the candle has indulged in " guttering " the cold drops 

 of grease will be found, in the morning, coloured green 

 by the metal dissolved. 



Another essential condition is, that it must have no 

 drying tendency. Every one know/s that there are two 

 classes of oils. The one known as drying oils greedily 

 absorb oxygen from the air, and pass into a resinous sub- 

 stance. Such oils are used for mixing paints, for the pre- 

 paration of varnishes, etc. The other class comprises those 

 which are used for burning in lamps, for lubricating 

 wheel-work, etc. 



The third property is the absence of fats — stearates 

 — capable of becoming solid at a low temperature. 

 For this purpose the oil is exposed to an intense 

 degree of cold, natural or artificial, when the stearine 

 compounds separate out, leaving a liquid portion safe 

 for use even with the most delicate machinery. The 

 process of refining these oils is very slow, two years being 

 necessary to submit them to all the tests required to in- 

 sure the limpidity and non-drying conditions necessary 

 to withstand the effects of changing climates which 

 chronometers and watches are subjected to. 



Our illustration represents a very extraordinary catch 

 of " black-fish " which was effected about two years ago 

 on the coast of Massachusetts. A large " school " of 

 these whales was seen to approach the shore, and imme- 

 diately some fishermen followed them, and succeeded in 

 driving them into bays and creeks where the receding 

 tide left no less than 2,200 an easy prey. These whales 

 were bought by Mr. Nye, of New Bedford, who obtained 

 from them some excellent lubricating " watch " oil, some 

 of which is now being used for the famous clock of the 

 Strasburg Cathedral. 



THE MIGRATION OF BIRDS. 



The naturalist who looks at the phenomena of migra- 

 tion from a single observing station, finds it con- 

 venient to distinguish certain common birds as 

 summer or winter visitants, others as transient visit- 

 ants, while yet others are relatively permanent. 

 The landrail and cuckoo come to us in spring to 

 spend the summer ; the fieldfare comes in autumn to 

 stay the winter. Some of the sandpipers flit along our 

 shores every spring and autumn on their way to distant 

 lands, while the rook and jackdaw are believed to stay 

 round the year about the same elms or church-towers. 

 Minute observation shows that the birds reputed to be 

 permanent are not so settled as the name implies, while 

 the class of " partial migrants," which never completely 

 disappear, though many individuals change their quarters, 

 is a considerable one. The song-thrush, redbreast, pied 

 wagtail, and woodcock are examples of partial migration. 

 In most parts of the country they may be seen in any 

 month of the year, and yet they travel to and fro in con- 

 siderable numbers, seeking food and shelter according to 

 the season. The robins which haunt our gardens in 

 summer are not always, or usually, the very same 

 individuals who come to our windows for crumbs when 

 the snow is on the ground. 



Though the summer and winter visitants are so easily 

 picked out, and though the motive of their migration 

 seems at first sight materially different, a wider expe- 

 rience than is to be got in our country shows the move- 

 ment is of the same kind in each case, and due to the 

 same cause. Both summer and winter visitants move 

 northward for breeding, and southward as the cold of 



winter approaches. Their ranges may differ extremely, so 

 that the northern limit of one species approaches the 

 southern limit of another, but this is by no means always 

 true. The " transient migrants " come to us on their way to 

 other countries, and stay so short a time that they are 

 called rare birds. 



It has long been known that the journeys of migrating 

 birds are in some cases of immense length. The 

 swallows nest in North Europe and winter in Senegal ; 

 certain cuckoos visit New Zealand every year, winging 

 their way over the vast southern ocean ; and the curlew 

 sandpiper, which nests on the shores of the Arctic Sea, 

 makes its way annually by India and Australia to the Cape. 



Palmen has shown that the migrating birds follow 

 defined routes, keeping to coast-lines or to great rivers. 

 They are thus enabled to find their way more easily and 

 to pick up a better supply of food as they travel. 

 Palmen's chief routes are described by Professor Newton, 

 in the new edition of the " Encyclopaedia Britannica" 

 (Art. " Birds.") The migrants form vast flocks, often 

 consisting of several species intermixed. They rest by 

 day, and fly by night, using the dark hours when food 

 cannot be found, to make progress with their long 

 journey. The cock birds are believed to arrive first in 

 spring, starting some days or even weeks before the hens. 



Wallace, and many naturalists before him, have dis- 

 cussed the causes of migration. Scarcity of insect-food in 

 the winter of northern lands, and the advantage of vast, 

 solitary wastes for rearing the young in summer, are the 

 most obvious grounds. Since these conditions are indefi- 

 nitely variable ; it is probable that every gradation exists 

 between complete coincidence of the "area of subsistence " 

 with the " breeding-area," and complete separation. 



The reports on migration of birds, published for 

 several years past by the British Association, contain 

 many curious facts. We learn, for example, that great 

 flocks of rooks, grey crows, and other birds reputed to 

 be permanent, may at times be found on the wing, 

 passing to and fro between England and Germany. The 

 same reports give graphic pictures of the vast numbers 

 of birds in a migrating army, and of the density of the 

 crowds which on a dark night dash themselves against 

 the lantern-windows. Much has already been learnt by 

 observations made at these numerous and well-placed 

 stations, and whenever the results are compared and 

 reduced, we may hope to be enlightened on many points 

 which are now dark or uncertain. 



A Rare Bird in Cumberland. — In the Ibis for January, 

 the Rev. H. A. Macpherson reports that an example of 

 the isabelline wheatear (Saxicola isabellina) was shot at 

 Aigle Gill, near Allonby, on the nth November last 

 (1887). This bird, which is new to Western Europe, 

 was observed by Messrs. Mann, who had a few days 

 before been requested by Mr. Macpherson to search for 

 doubtful wheatears. The light colour of the bird attracted 

 their attention, and it was shot by Mr. Thomas Mann, 

 and sent the same day to Mr. Macpherson. Mr. Seebohm, 

 Mr. J. E. Hartine, Mr. Howard Saunders, and other 

 experts saw the specimen, and identified it as S. 

 isabellina. It was a female bird. It is worthy of remark 

 that another species of whatear new to this country — 

 the black-throated wheatear (Saxicola stopasiiia) — was 

 shot near Bury, Lancashire, on the 8th May, 1875. 

 This, as Mr. Mitchell points out in his "Birds of Lanca- 

 shire," is the only example of this Southern European 

 species which has yet occurred in Britain. 



