254 



KNOWLEDGE. 



[November 1, 1899. 



shells, also chanced upon, may possibly yield interesting 

 records. The dwelling ante-dates the Eoman occupation 

 of Britain, but does not seem to go back further than 

 Celtic times. The piles are accurately sharpened by 

 bevels on four sides, and the tops are occasionally squared. 

 Excepting that the workmanship is less primitive, the 

 Hedsor settlement seems to be constructed on the same 

 plan as that at Braintree (the first inhabitants traced here 

 were certainly Neolithic men), for the piles cannot be made 

 to correspond with any supposed individual dwellings, and 

 were driven into the mud to hold in position, apparently, 

 an artificial island, with a floor of branches and earth 

 raised above the water on which the huts were built. Only 

 a small watercourse (Blessing's Ditch), which runs 

 through the site, marks the direction once taken by a larger 

 tributary of the Thames that now flows into the river 

 higher up. Its waters must in olden times have sur- 

 rounded the settlement, and the causeway leading from the 

 latter to the dry land has been followed for some distance. 



— - « ♦ » 



The arrangement of a collection illustrating the modifi- 

 cations of animals that have followed upon domestication 

 has been begun at the British Museum (Natural History), 

 and already a number of interesting stuffed specimens and 

 skeletons have been placed on exhibition in the gallery 

 of British zoology. These include several celebrated dogs, 

 such as the greyhound " FuUerton," as well as a series of 

 South American sheep with four or more horns. 



We notice that Mr. J. H. Steward, the well-known 

 optician, has just put upon the market a very elegant and 

 eiieotive equatorial telescope suitable for araateurs, at a 

 price within the reach of all earnest students of celestial 

 objects. Lightness and ease of manipulation are secured 

 without sacrifice of rigidity — a quality which all practical 

 workers can fully appreciate without further amplification. 

 The motion in right ascension is controlled from the eye- 

 end by means of a long handle provided with a Hook's 

 joint, and the clamp for the declination axis is also worked 

 from the eye-end of the telescope. By means of a vernier 

 the declination of an object can be read to five minutes of 

 arc, and the hour circle to twenty seconds. 

 — ^-.-. — 



Dr. Eoss, who was sent out to Sierra Leone by the 

 Liverpool School of Tropical Diseases, to trace the cause of 

 malaria, says in a letter; — " For many scientific reasons we 

 have come to the conclusion that the truly malarial fever is 

 caused here solely by the mosquito — probably entirely by 

 the Anopheles species. We estimate, then, that most of 

 the malarial fever here can be got rid of at almost no cost, 

 except of a little energy on the part of the local authorities." 

 Perhaps the most encouraging part of Dr. Ross' letter is 

 that in which he says the destruction of the peccant insects, 

 in the puddles in which they spend their larval stage, can 

 be effected by an agent so comparatively harmless as 

 kerosine. For a history of the relations between mosquitoes 

 and malaria, we may refer the reader to an article by 

 Mr. Percy H. Grimshaw, printed in the March, 1899, 

 number of Knowledge. 



RECENT WORK OF THE UNITED STATES 

 BIOLOGICAL SURVEY. 



By WiLFBED Mark Webb, k.l.s. 



NATURALISTS are beginning to look forward to 

 the interesting as well as useful researches made 

 from time to time by the Biological Survey of 

 the United States. The survey forms a division 

 of the Department of Agriculture, whose year- 

 book has been recently issued. In this volume, among many 



valuable papers, we find several contributions from 

 biologists. 



The first one that we will mention has the title of 

 " Birds as Weed Destroyers, " and is written by Dr. Judd, 

 who, it will be remembered, so well weighed the evidence 

 for and against the usefulness of shrikes. Of particular 

 interest is it to us in view of the many attacks upon the 

 character of the English sparrow to hear what this impartial 

 judge has to say about the members of this species, now so 

 thoroughly established in the United States. Dr. .Judd 

 says with regard to the native American sparrows that they 

 have been collected in practically all the States, in the 

 district of Columbia, and in Canada. Their stomachs, to 

 the number of four thousand, were examined previous to 

 the writing of his paper, and it was shown that during 

 the colder half of the year the food of these birds is 

 practically made up of the seeds of weeds. 



This would lend considerable support to the general idea 

 that the native sparrows ai'e useful, while the English one, 

 seeing that it drives the others away, might for that :done 

 be reasonably regarded as a pest. Now as to the other 

 charges against Passer domesticus. A number of birds, 

 including five specimens of our and nineteen of the 

 American sparrows, were collected in a cornfield. All the 

 former were gorged with wheat, while only two of the 

 latter had touched the corn, and then had only partaken 

 of a single gi-ain in each case. 



Still. Dr. .Judd has a good word to Bay even for the 

 English sparrows, for they destroy large quantities of 

 weed seeds. He says that they come in thousands to 

 the lawns of the Department of Agriculture, and feed on 

 the grams of two useless grasses which crowd out the 

 ones better adapted for making turf. We are also glad 

 to hear that they make many a meal of dandelion 

 fruits. 



Several native birds, such aa the song sparrow {Melospiza 

 fasciatii), the chipping sparrow (SpheUa ■■iocialis). and the 

 \vhite-throated spaiTow [Zonotrichia albicolUs), help the 

 English species in his work of destruction. They usually, 

 however, leave the hardest part of the task to him, and do 

 not open the heads themselves, but seize the exposed 

 fruits or pick up those which have been dropped by their 

 cousins. The latter adopt the following method of securing 

 their food : — Several of the green outer bracts are removed 

 by being cut through close to the swollen part of the stalk 

 or receptacle to which they are attached. The heads 

 selected are those from which the yellow strap-shaped 

 corollas of the florets have disappeared, while from the 

 closed protective bracts, the down-like calices project that 

 ultimately would spread out and form the miniature para- 

 chutes that carry away the one-seeded fruits on the 

 wings of the wind. The removal of the casing exposes 

 the down, and below this the fruits; a mouthful of the last 

 is Sfized by the bird, who separates the down from them 

 by a movement of his beak and swallows them. When a 

 bird is hungry, however, it may not pause to remove the 

 downy tufts, and these are eaten too. 



To return to the native birds, although a song sparrow 

 in captivity was able to secure the fruits in the same way 

 as its English relative, yet, as mentioned previously, in 

 a wild state it does not take this trouble. The goldfinch 

 {Astragalimis tiistu) has a different plan ; it waits until a 

 head is ripened sufficiently to open once more, and alighting 

 upon the stem of the latter the bird moves towards it 

 so that it is bent down to the groinid, as shown in a 

 pretty vignette. In this position a meal is easily obtained. 

 Prof. Beal, after careful observation in the Upper Missis- 

 sippi Valley, says that the tree sparrow (Spizella monticola) 

 must eat at least a quarter of an ounce of weed seed per 



