Jax. 2 7, 1882.J 



KNOWLEDGE 



275 



Take the word Enorgj'. We hear of energy " poured into," 

 "taken from," " transferroil," ** accnraulated," "wasted,'* and so 

 on. What wonder that many should regard " energy " as some- 

 thing having as substantial an existence as a glass of wine. So 

 with the langnago used in describing the so-called electric " accu- 

 mulators" and "storers." Ninety-nine hundredths wlio read 

 about the Fanrc accumulators suppose that a real substance called 

 electricity is jjoured, which can be tapped like beer from a barrel, 

 that a Fauro accumulator is as innocent of containing any electricity 

 as the Meteorological (lffice|is of knowing how to make weather fore- 

 casts, — it is not a container of, but a producer of, electricity — that 

 it consists of lead plates j)ractically double, back to back, the one 

 side being electro-positive, the other electro-negative ; and that it is, 

 in fact, nothing different iu the principle of its action, from an 

 ordinary galvanic cell. 



There ia no need for this foolishly figurative language. The dis- 

 covery is as wonderful, when described as an improved method of 

 preparing plates for the generation of electricity, as when called, in 

 inflated language, " a method of carrying so many millions of 

 foot-pounds of energy from London to Edinburgh, <ic." 



Edmixd p. Foy. 



PERSOX.U, IDENTITY i: TATTOO MARKS. 



[236] — Physiologists admit that the human body is in a constant 

 State of change, fresh materials being added and fresh waste re- 

 moved, in fact these are the characteristics of evcrj- living organism ; 

 but that a complete change and reconstitution of the body takes 

 place every seven years will, I am afraid, be admitted by very few. 

 In old age it may take longer than seven years, whilst in disease 

 and in those who live dissipated lives a much shorter period will 

 suffice. Mr. Magtiii-e inquires whv it is tattoo marks do not dis- 

 appear. I will endeavour to answer his query. Tattoo marks .ore 

 produced by making small punctured wounds into the true skin with 

 sharp needles dipped in some colouring matter. Slight inflammation 

 is produced, but soon passes off, leaving the colouring matter en- 

 cysted permanently in the substance of the cutis vera and cellular 

 tissue below it. The colouring material used is insoluble as carbon, 

 Vermillion thence cannot be taken up by the absorbents or lym- 

 phatics and e.tcreted from the body by the excretory glands. 



Occasiiinally tattoo marks do disappear. M. Hutin found that 

 out of seventy-eight persons tattooed with vermilion, the marks 

 disappeared in eleven ; and out of 104 tattooed with China ink, not 

 one had become obliterated. The cases where the marks have dis- 

 appeared have been due to their having been inefficiently performed, 

 and not to the colouring matter having been removed by the 

 lymphatics. This only occurs when soluble and fugitive colours are 

 used, and when the surface of the cutis only is penetrated. 



Chas. Boyce, M.B. 



TELESCOPE. 



[237] — I am contemplating the expenditure of from £iO to £60 

 or so in a telescope and accessories. Perhaps some of your numerous 

 correspondents, and notably " A Fellow of the Royal Astronomical 

 Society," would not object to give a little aid in the way of laying 

 out my money to the best advantage. I am an amateur, and that 

 only, and likely so to remain, as my time available for astronomy 

 IS verj- limited. I should, however, like an instrument that would 

 take me well through Webb's " Celestial Objects," and one which 

 would be of real use to me in case at any time hereafter I might 

 have more time to devote to the subject. I am doubtful as to 

 whether a Reflector or Refractor would best suit my purpose. The 

 gl^t objection to the former seems to be that it must almost neces- 

 sarily be a fixture, and this would scarcely suit me at present. 

 Heither is it so handy. Countby Solicitob. 



HOW TO CONSTRUCT A TELESCOPE. 



[238] — The astronomical papers now running a course in this 

 magazinaVhave, no doubt, induced many readers to begin ft tele- 



IBoopio scrutiny of the skies. Pecuniary considerations, however, 

 •nay have affected the number of astronomical recruits, and, there- 

 fare, I think it not uncalled for to show how one may become 

 possessed of a good three-inch telescope at a comparatively trifling 

 cost. In the beginning of last year I succeeded in making an 

 effective telescope of that size, and where I have succeeded very 

 ] few need fear failure. Its cost was inconsiderable, and I shall bo 

 I glad if the follomng short account of its construction encourages 

 anyone to make a similar attempt. 



Having ascertained the dimensions of a 3 in. telescope, I got a 

 carpenter to make several cyUndric moulds, the largest being 34 in. 



in length and 3^ in diameter; and upon this mould I made the 

 principal tube, employing in its construction nothing but the 

 stoutest and largest-sized cartridge paper and an unlimited supply 

 of thick floiu- paste. The method was as follows : — As much of 

 the first sheet as formed the internal circumference of the tube was 

 painted dead black, and wound, not too tightly, round the 

 mould, the second layer being formed by tho continuous 

 winding of the flrst sheet. No paste was used for tho second 

 layer, in order that the inside of tho tube might not be blis- 

 tered, a slight touch of paste being given where the sheet 

 overlapped and ended. Then two sheets at a time were wound 

 round as evenly as possible, paste being laid on with n liberal 

 hand, and each layer allowed to dry thoi-oughly before winding 

 on its successor. This process was continued until a thickness of 

 over one-eighth of an inch was reached ; und when removed from 

 the mould, and carefully evened at the ends, I had a light tube. 

 29 inches in length, and as hard and smooth as the tube of a 3-inch 

 telescope need be. It is astoni.shing how hard pastcboartl can be 

 made when good jiaperand plenty of paste are used. (I may mention, 

 as a warning, that the removal of the tube from tho mould was 

 somewhat dilBcult, as the contraction of the paper has been greater 

 than allowed for.) The other tnbes, of which details are given 

 below, were made in the same way, and of nearly the same thick- 

 ness. The method of fitting the pieces together will be readily 

 understood from the following longitudinal section of the instru- 

 ment : — 



It will bo seen that tho telcRcopo has two " draws," B and C, 

 which slide in fixed tubes, D and E. Hound the middle of the 

 fixed tubes strips of paper 2 inches in width for tube D, and 1 inch 

 for tube E, are firmlj- pasted, forming bands of sufficient diameter 

 to fit the tubes into the ends of which they are fixed. The fixed 

 tubes are thus tightly fitted, and are held in their places by small 

 brass screws. The second draw, C, is a short tube, whose diameter 

 is just sufficient to admit the tube of the eye-piece. The draws :ire 

 fitted vnth stops, and the order in which the various pieces have 

 been placed together is obvious. Each part was allowcil to dry and 

 contract thoroughly before being fitted. A brass screw is fitted 

 into the mouth of the tube, and receives the screw attached to the 

 cell of the object-glass. I may mention that, for the sake of appear- 

 ance, the telescope is covered with dai'k-coloured imitation morocco. 

 The dimensions are as follows :■ — Tube A, length 29 inches ; internal 

 diameter, 3^ inches. B, 10 and 2i inches. C, 54 and li inches. 

 Fixed tube D, length 6 inches, projecting 2 inches beyond end of 

 tube A. Fixed tube E, 6 inches, projecting 1 inch. Focal length, 

 over 41 inches ; closed, under 34 inches. 



When the various tnbes, &c., were completed, glasses of first- 

 rate quality were purchased, and the whole ])arts put together and 

 carefullj- adjusted. There is little or no vibration. 



Tho mounting of the telescope was a simple matter. For out- 

 door work a tripod garden stand and cradle was purchased, and for 

 work indoors a pillar and claw-table was seized, the toj) removed, 

 and, with a little trouble, fitted so as to receive the cradle of the 

 garden stand, and the claws loaded with load, for the sake of 

 steadiness. Including the extra expense caused by bungling and 

 ignorance, the total cost of the instrument was about ,£12. The 

 table stand, it must be remembered, however, cost only a. remon- 

 strance. 



I need hardly say that in the course of its construction I 

 enjoyed many distinguished failures; parts were made and remade, 

 fitted and re-fitted before all defects were rectified and the instru- 

 ment entitled to rank as a telescoin;. Its appearance may not bo 

 sraai-t, but a telescope is handsome according to its performance. 



A. P. JI. 



COLOURS OF STAMENS.— ORIGIN OF EVERGREENS. 



[239] — Mr. T. Dowse's objection [214] to my theory that flowers 

 wore all originally yellow, has already been advanced in a private 

 letter by Mr. Darwin (who, I am glad to say, is inclined to agree 

 with my general view that petals are derived from flattened 

 stamens). Still, I feel disposed, in spite of such an authoritative 

 critic, to adhere to my first statement. It is true the filaments of 

 many stamens are white, pink, or purplish ; but this is the case 

 chiefly (so far as I have observed) with verj- highly developed 

 flowers, in which the petals have undergone much change of colour. 

 It is especially noticeable in tubular blossoms. On the other hand, 

 most very simple flowers, such as buttercups, have bright yellow 

 filament.i, and my general impression has been that petalless 

 flowers (for example, catkins) usually have yellowish stamens. The 

 point is an important one, and I will make definite observations 



