3°4 



SCIENCE-GOSSIP. 



when the water at the top of C is sometimes as 

 much as io° hotter than that issuing from G. 



The support shown in fig. i will be found very 

 convenient, as all its parts are adjustable, and as 

 the condenser holder and other fittings are 



clamped on a tube which slides over the iron 

 rod of the stand, the whole arrangement can be 

 raised or lowered by one operation at the con- 

 venience of the operator. 



{To be continued.) 



INSTINCT. 



By R. Dickson-Bryson, B.A., F.P.S., F.RAs.S. 



(Continued from page zyo.) 



"DIRDS show in the construction of their nests 

 similar care and skill, and with the same 

 perfect tools. What could be less fitted for build- 

 ing nests, considering their almost endless variety 

 and adaptation, than the beak, feet and body of a 

 bird ? Yet in spite of these limited means, the 

 bird sews, weaves, pads and builds. Note too, 

 each species has built on the same uniform plan 

 from immemorial time. 



The feathered race is aerial, somewhat as we say 

 fishes are aquatic. The aerial empire is their free 

 and undisputed possession. They are sociable and 

 friendly and appear to exchange greetings with one 

 another. Their sharp eyes enable them to see near 

 and distant objects with marvellous facility. They 

 build their nests at the same time of the year, with 

 nearly similar material and with the same instru- 

 ments — the beak and claws ; yet their nests vary 

 and are characteristic of each species. Qitalis avis, 

 talis nidus. No one could mistake the swallow's 

 nest (Hirundo domestica) for that of the bullfinch 

 (Pyrrhnia), nor these two for that of the wren 

 {Troglodytes), and so with many others. In spite of 

 their inter-related life and habits and similarity 

 of organs they never copy nor borrow from one 

 another. There is among birds, as among beavers, 

 the same immutable, perfect, specific and in- 

 transmissible instinct. 



No one can have failed to note the skill, energy 

 and patience displayed by swallows in nest build- 

 ing. Soon after their arrival from the South they 

 begin to build their nests and to repair those they 

 occupied the preceding year. A common sympathy 

 appears to lead them to a mutual assistance of one 

 another. Those having fewer demands on their 

 time assist their busier companions. 



House-martins having selected sites for their 

 future homes, begin building operations at once. 

 They carry the mud destined for building in their 

 beaks. It is moistened and rendered adhesive by 

 means of the viscid saliva it secretes. To render 

 it more tough when dry it is mixed with pieces of 

 straw and wood, and in fact with anything that 

 will enable the mass to cohere. The first beakfuls 

 are applied to the wall, generally in a corner, and 

 under the eaves ; this serves as a foundation. 



Each new beakful is applied to the other, and 

 so the walls, slightly curving, increase until they 

 meet. The shape is usually hemispherical. At 

 the top a small aperture is left, which serves as an 

 entrance. It is then lined with down and made 

 comfortable and snug for the reception of the 

 young brood. 



The tailor bird (Orthotonus) is a well-known 

 native of the tropics, and owes its name to its 

 sartorial proclivities. Its curious nest is formed 

 of leaves sewn together. It detaches a leaf from 

 the tree and sews it to another, edge to edge, 

 perforating the leaf with its bill, and inserting 

 the thread, a vegetable fibre which it prepares, 

 into the opening thus made. Between the leaves 

 thus arranged is a small cavity which, when lined 

 with soft fibre and down, constitutes the nest. 

 When complete it is not easily distinguishable 

 among the foliage, and so the tailor bird and 

 family escape from their enemies. 



The weaver birds suspend their nests in a curious 

 fashion from the end of flexible branches over- 

 hanging rivers and lakes. By this artifice they 

 enjoy a merited immunity from their enemies, 

 such as snakes, squirrels and monkeys. To 

 suspend her nest the weaver bird collects a quan- 

 tity of grass and vegetable fibre with which it 

 plaits a sort of cord. This it securely fixes to the 

 branch selected, and to the free, pendulous end it 

 weaves its nest. When complete the nest resem- 

 bles a bottle in shape. The entrance is at the lower 

 end. The nest is suspended like a fruit with a long 

 peduncle. The weaver bird's nest is a marvel of 

 instinctive skill, and its enemies are unable to 

 reach it. 



It would be superfluous to multiply examples ; 

 we have stated enough to show that each species 

 has its own characteristic type of nest, and that, 

 notwithstanding the identity of materials, organs, 

 and purpose. Instinct, and absolutely nothing of 

 reason, is the dominant factor in nidification. We 

 cannot on any known theory account for the 

 variations arising from climatic, local and other 

 accidental circumstances. These variations be- 

 speak a purposeness behind all, which the super- 

 ficial philosophy of to-day calmly ignores. 



