62 



KNOWLEDGE. 



[March, 1902. 



THE USE OF HAND TELESCOPES. 



TO THE EDITORS OF KNOWLEDGE. 



SiBs, — In tlio article "The Use of IlaiiJ Telescopes in 

 Astronomv " in tbis month's Knowledue it is said that 

 in order to increase the jwwer of the instrument it is 

 desirable to remove the lens next but one to the eye end. 

 I have tried this with my telescope, which is a three-draw 

 one, IJ in. object glass, and found the result tolerably 

 satisfactory. 



However, a much better plan is to remove the third 

 lens, i.e., the next but one to the object glass, the result 

 was a suri>risinL;ly good one, every part of the field of 

 view available for distinct vision, and the magnifying 

 power about half as large again. 



The holding and steadying of a small telescope out of 

 doors is a great trouble even for ordinary use, and always 

 a failure when observing celestial objects. So I got a 

 clip made with a screw attached to it, by means of which 

 I can steady the telescope, and move it freely in every 

 direction. 



I also have an astronomical telescope with a 3 in. oljject 

 glass and a power of 100 diameters, and I find it often 

 useful to remove the inner one of the two lenses which 

 form the eyepiece. The field of view becomes smaller, but 

 the magnifying power is very much increased thereby, and 

 it enables me to see eomparatively very small objects on 

 the moon, and even divide the rings of Saturn. 



Walthamstow, February 10th, 1902. M. Haee. 



[I do not agree with Mr. Hare as to the great advantage 

 to be attained by removing the third lens from the eye end 

 — the next but one to the object glass — though the field 

 is better than when the lens next but one to the eye 

 end is removed. But the advantage of using some means 

 of steadying the telescope is very great. Only, though 

 this is but a verbal criticism, it could scarcely then be 

 described as a "hand telescope." — E. Walter Maunder.] 



A METHOD OF GENERATING ACETYLENE. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — The following method of generating acetylene in 

 small quantities, which other boys and myself have used 

 for some time in the Chemical Laboratory, at Mill Hill 

 School, may be of interest to readers of Knowledge. 



Place a few lumps of calcium carbide in a six ounce 

 flask or Woulfi's bottle, and cover them with methylated 

 spirits. If diluted hydrochloric acid (1 : 2 water) be 

 slowly dropped into the bottle by means of a stoppered 

 funnel, a steady flow of acetylene gas is evolved, which 

 can be collected, like hydrogen, over water. 



The equation is — 



Ca C, + 2 H CI = Ca CLj + Co Hj. 



The advantages of this method as compared with that 

 given in text-books (dropping water upon dry calcium 

 carbide) are — 



(1) A steady even flow, completely under control, 

 instead of a rapid, brief evolution ; 



(2) A liquid mass of calcium chloride left, easily 

 washed out of the bottle, instead of a hard cake 

 of slaked lime. 



It was not found practicable to keep the calcium carbide 

 under alcohol for any length of time, as the mixture 

 slowly evolved acetylene. 



It is possible that the method may be of practical utility 

 for cyclists' lamps, although the use of acid might necessi- 

 tate some alteration in the material of these. 



Mill Hill School, N.W. 



E. Knowles. 



BRiTIStt 





ORNiTHOLOGlCA 



* v 



.NOIiSr:-^ 



Conducted by Habby F. Withebbt, f.z.s., m.b.o.u. 



Possible Sreeding oj the Eared Grebe in Oxfordshire (.Ibis, 

 January, 1902, p. 165). — Mr. O. V. ApUn writes to the Ibis with 

 regard to a pair of Eared Grebes which were shot on a large poud 

 near Blo.\haia on September 19th, 1899. Mr. Aplin gives reasons for 

 supposing that these birds mav liave remained to breed in England, 

 and that they were not merely migrants. 



Nutcracker in Herefordshire {Zoologist, January, p. 2.5). — Mr. 

 H. E. Forrest records tliat a Nutcracker was obtained in September 

 la«t near Hereford. In view of the in-uption of the Siberian form of 

 the Nutcracker into Western Europe in the autunm of 1900 (see 

 Knowledge, 1900, p. 256; 1901, pp. 117 and 281), it would be 

 interesting to know if this specimen was of the slender-billed Eastern 

 form. 



King-Eider in Fifeshire {Zoologist, January, p. 27). — Mr. B. B. 

 Kiviere records that a male King-Eider was shot on a moor in Fife- 

 shire on Jime loth, 1899. This Arctic bird seldom visit* our islands. 



Tengmalm's Owl in Suffolk (The Field, February 1st, p. 177). — 

 Mr. F. W. Frohawk here gives an account of two specimens of 

 Tengmalm's Owl which were picked up in an exhausted state at the 

 end of last October in Suffolk. One of the birds was picked up by 

 Captain Lawrence Grubbe on the beach at Southwold on October 

 30th. The other bird was found in the gardens of the Grand Hotel 

 in the same town probably about the same date. Both birds have 

 been kept alive, and are remarkably tame ; but neither give any indi- 

 cations of having been in captivity. Tengmalm's Owl is a rare visitor 

 to the British Islands, and most of the records have been from the 

 Eastern Counties during the autumn or winter. Tliis Owl is an 

 inhabitant of the pine forests of northern regions, but it is also 

 found in the pine-clad mountains of the south ; and it migrates to a 

 considerable extent during tlie autumn and spring. 



...■'.,. Diirinij the absence from Em/land of Mr. Harry F. 

 WiTHERBY, who has started on an Ornitholo(iical E.vpeditio7i 

 to South-West Persia, these Notes iiill be eondiuted by Mr. 

 W. P. Pycr.\ft, to whom all communications should be addressed 

 at the Natural Histor;/ Jtluseum, Cromwell Road, London, 5.11'. 



Astronomical. — From measurements made at the 

 Lick and Yerkes Observatories, Prof. Barnard has deduced 

 the following values for the diameters of planets and 

 satellites : — 



