February i8, 19 15] 



NATURE 



^73 



natural history-, it is found that many are copied after 

 drawings in old manuscripts. 



A good example is furnished by Conrad Gesner's 

 figure of an ichneumon, taken from an ancient MS. 

 of Oppian, as the author declares. 



Fig. 1. — Giraffe from mural painting at Villa Pamfili, 

 near Rome. (After Keller, Irom Jahn). 



In the case of the giraffe, what is thought to be 

 the earliest portrait taken from life and engraved in 

 a printed book, occurs in a work published in i486 

 by Bernard de Breydenbach, a canon of Mayence, 

 under the title of '-'Opusculum sanctorum perigrina- 



num." The figure is, however, inferior to those 



antiquity, and still earlier designs have come down 

 to us in the form of ancient Egyptian hieroglyphics 

 and inscriptions. That some of these were remark- 

 ably faithful likenesses may be judged from the two 

 accompanying figures, one of which is reproduced 

 from O. Keller's "Die antike Tierwelt *' (1909), and 

 the other from a memoir by C. G. Ehrenberg, " L'eber 

 dem Cynocephalus und den Sphinx der Aegypter," 

 published in 1834. C. R. E.^st'man. 



American Museum of Natural History'. 



Fig. t. — Giraffe and Cercocebus, from ancient EgTptian 

 monument at Thebes. (After Ehrenberg). 



of the same and other African mammals which are 



introduced in the Ebsdorf and Hereford maps of 1282. 



Pictorial representations of the giraffe by Roman 



artists have been presers'ed from the time of classical 



NO. 2364, VOL. 94] 



The Economic Status of the Blackcap. 



Mr. Collinge does not meet the question whether 

 the good the blackcap does in the spring balances the 

 value of the fruit it takes in the summer. But he 

 mentions having found a few aphids in the stomachs 

 even in the fruit season, from which it may be in- 

 ferred that more would be eaten, when there was no 

 fruit in the spring. Now considering the enormous 

 reproductive powers of the female aphis and that everv' 

 female destro\'ed in the spring represents a diminu- 

 tion of many hundreds of the most mischievous pests 

 that the farmer has to contend with in the summer, 

 it seems only reasonable to conclude that the bird 

 does at least as much good as harm. But the latter 

 is seen while the former is not 



-\lfred O. W.alker. 



Ulcpmbe, Kent, February 5. 



My experience of the blackcap is that the good it 

 does in the spring by no means balances the harm 

 it does during the rest of the year in fruit-growing 

 districts. 



The aphids found in the stomachs were all pea lice 

 (Macrosiphum pisi, Kalt.), and were probably ob- 

 tained accidentally when feeding upon peas. 



I have elsewhere pointed out ijourn. Board Agric.., 

 Sept., 1912) that all birds, other than doves and 

 pigeons, feed their young upon an animal diet, of 

 which insects form a large proportion, whatever may 

 be the character of the food of the adult ; the blackcap 

 would, however, seem to form an exception, judging 

 from the four nestlings I examined, whose stomach 

 contents consisted of seeds or remains of fruit and 

 fruit pulp. W.\LTER E. Collinge. 



8 Newhall Street, Birmingham. 



The Rusting of Iron. 



I DO not know if any account of experiments such 

 as the following on the rusting of iron has appeared 

 in print before, but if not they may be of interest to 

 others of your readers besides myself. Briefly, they 

 are as follows : — 



(a) A small flask (100 c.c. flask with long narrow 

 neck does well) is filled to the bottom of the neck 

 with potassium ferricyanide solution, and then the 

 neck is filled to the top with ordinary water. .\ long 

 bright iron nail is then suspended in the water without 

 disturbing the ferricyanide solution, and in a few 

 minutes a blue colour will make its appearance in 

 the neighbourhood of the boundan,' between the water 

 and the ferricyanide. The formation of Turnbull's 

 blue goes on regularly, and it settles to the bottom 

 instead of iron rust. 



{b^ A bright iron nail is placed at the bottom of 

 a solution of potassium ferricyanide in a similar flask, 

 and in a short time spots of blue make their appear- 

 ance on the nail instead of the usual depyosit of iron 

 rust. 



The explanation according to the ionic theory seems 

 obvious. E. J. Sl'mxer. 



The Grammar School, Burnley, Lanes, February 5. 



