October, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



563 



pocket telescope, after once suitable conditions had 

 been found. In fact, it was quite possible to take suffi- 

 cient observations of the index oscillations from the 

 sixteenth of an inch divisions of a common foot rule, by 

 using a pair of opera glasses, to enable charts of luni- 

 solar \ ariations tO' be obtained. 



Of course, the earth and the pendulum ball both move 

 relatively to extra terrestrial bodies, and the recording 

 Oif earthquakes and tremors might more fitly be entered 

 upon when the larger regular changes are first recog- 

 nised and charted. Else the diurnal oscillations are 

 liable tO' confuse the earthquake oscillations. However, 

 these latter have not been my objective, and have not 

 obtruded upon my other work. 



It was most convenient to me tO' consider the pendu- 

 lum curves as affording comparative and undeniable 

 evidence in themselves without troubling as to whether 

 the ball was at rest and the building oscillating, or the 

 building at rest, and the ball oscillating, or as to 

 whether both were, and to what extent, oscillating. 

 In accordance with the same convention as that by 

 which we regard the (ircenwich Observatory at rest, 

 when observations are made through its large tele- 

 scopes, SOI far also I was entitled tO' consider the build- 

 ings at rest in which I made my observations. If they 

 moved, Greenwich Observatory (worse situated)* must 

 indeed, have executed serious oscillations involving all 

 its telescopic observations in error. 



The advantages of using this kind of pendulum I 

 found to be : (i) It can be made, fixed, and used in any 

 ordinary house, by a person of ordinary intelligence, 

 from common materials, for a few shillings. (2) It 

 gives direct readings, and therefore its evidence is 

 superior to such as might be got by using reflected 

 rays from Gauss mirrors, from photogranhic recording 

 instruments, or from counting oscillations, and calcu- 

 lating on the assumed accuracy of certain formula?, and 

 so on. (3) There are no' restrictions whatever as to its 

 use, such as patent rights or aught of that kind. 



I am not aware of any better means of investigating 

 gravitation, and I say this after having been engaged 

 therein more or less continuously for forty years, solely 

 on my own account, independently, and after recent en- 

 quiries as to what others have done in pendulum con- 

 struction and use. 



I use three pendulums simultaneously, one in the 

 meridian plane, one in a plane at right angles thereto, 

 and one with means of observing vertical component. 



VoH Rcheiir Faschwiiz's Pendulum (1892). — This 

 so-called horizontal pendulum also has a " two point " 

 lateral suspension. Tlie rod is replaced by a triangular 

 frame after the style of Kwing's seismograph aforesaid, 

 which it much resembles, though it is alleged to have 

 been based upon Zollner's pendulum, which it does not 

 resemble save perhaps in regard to the use of a Gauss 

 mirror, and angular deviation therewith of a ray of 

 light. In fact, it is a seismograph, and has been very 

 widely adopted for seismographic purposes, although 

 Paschwitz himself made observations with it upon the 

 variations of gravity, etc. (see Fig. 10). 



It must be understood that in using pendulums of any 

 ol the above descriptions involving points working upon 

 bearing surfaces, the rod may have the point, and the 

 wall or support mav have the be.'iring' surface, but if 

 more convenient, the rod may have the bearing surface, 



• My latest observations were made here in 0° 3' E. Lon., 51" 

 32' 40' N. Lat., 19 feet above Trinity liigli water mark and three 

 miles from nearest part of tidal river Thames. 



and the wall or support may have the point. Also it 

 is obvious that any pendulum may have a Gauss mirror 

 attached, in order to use the angular deviation of a ray 

 of light or reflected scale image for magnifying its 

 motion, and that recording apparatus of any kind — 

 automatic, photographic, or otherwise — may be used as 

 convenient. Stands, set screws, and levelling or ad- 

 justing devices are useful, but by no means necessaiy. 

 I prefer tO' use aluminium, or brass tube for the " rod " 

 or " boom." 



There is no doubt that each of the pendulums herein 

 named were independently invented to suit the special 

 enquiries, available materials, and environment of their 

 inventors, as the literature of pendulums is compara- 

 tively limited, and what there is of it is very difficult to 

 find, and almost inaccessible, owing to the vast ac- 

 cumulation of literary matter in which it is buried in 

 different places over a very great area. 



.\t a future date, with the editor's permission, I mav 

 give some charts of lunisolar observations, taken with 

 my pendulum, and give the results of my experience 

 as regards the best method of erecting, adjusting, and 

 using pendulums for making same. 



CORRE SPON DENCE. 



Electrical Nitrates and Fertilisers. 



To the Editors of " Knowledge & Scie.ntific Nkws." 



Sirs, — The article under the above heading in your last 

 issue opens with the following sentence : — 



"At present the world's wheat supplv depends chiefly 

 on the continued productiveness of a strip of territory in 

 Chili." 



With all due deference to the writer of the article, I would 

 point out that this statement is very far from being correct. 

 Nitrate of soda is, no doubt, being worked in increasing 

 quantities in Northern Chili, and there is a large demand 

 for it as an artificial manure. Probably less of this fertiliser 

 IS, however, applied to wheat than to any other important 

 crop._ Nitrate of soda in British farming is applied 

 principally to turnips, mangels, cabbages, and grass, much 

 less commonly to any corn crop. 



Wheat is in no sense dependent for its profitable cultiva- 

 tion upon nitrate of soda. 



The value of calcium cyananide as a nitrogenous manure 

 as compared with sulphate of ammonia has" been tested at 

 Rothamsted Kxperimental .Station, and an account of the 

 experiments will bo found in the "Journal of the Board 

 of Agriculture," for July last. 



I am, vours etc., 



J. H. .M. H. 



Electrical Bleaching. 



There is good reason for believing that the excessive whiten- 

 ing of flour deprives it of its nutritive qualities. Neverthe- 

 less, devices for bleaching it continue, and an electrical 

 method is cheap and is said to be successful. .\ current of 

 air is passed through a closed chamber, in which is a Ion"- 

 high-voltage electric arc. The air thus electrically burnt il 

 then passed through the flour as an agitator, and becomes 

 whitened in the process. Presumably "the discharge of the 

 electric arc produces compounds of nitrogen and o.Kvgcn in 

 the air which act as bleaching agents. This nie'thod is 

 osseiuially dilTcront from the other electric processes of 

 bleaching flour by ozonising the air passed through it. In 

 that process the air passes through a chamber" in which 

 there is a silent electric discharge. .\ combination of the 

 two processes is suggested, the ozonised air being subse- 

 quently burnt by the arc discharge. A machine has been 

 patented, and is actually in use. 



