May 8, 1879] 



NATURE 



35 



actual conformations of the great terrestrial divisions of 

 land and sea, arcs of longitude are, I imagine, especially 

 likely to be affected by such causes. 



The views which I have now attempted to express are 

 by no means new, but it has not appeared necessary to 

 cite authorities. I am indebted to many writers, but I 

 should be sorry to have to assign to each the measure of 

 the influence which his learning has had on the drawing 

 up of this brief, which 1 hope some geodesist will now 

 take up and argue more fully and more ably. 



Dehra J. Herschel 



THE ROYAL SOCIETY SOIREE 



ON Wednesday last week the President of the Royal 

 Society gave a soiree at Burlington House, which 

 was largely attended, and at which a considerable variety 

 of apparatus were exhibited and many experiments made. 

 Mr. Crookes showed his exhausted tubes and other appa- 

 ratus, illustrating various phenomena connected with 

 molecular physics in high vacua. The experiments made 

 by these were the following :— 



1. Dark Space round the Negative Pole. — When the 

 spark from an induction coil is passed through an ordi- 

 nary vacuum tube, a dark space is seen round the negative 

 pole. The shape and size of this dark space do not vary 

 with the distance separating the poles ; nor, only very 

 slightly, with alteration of battery power, or with inten- 

 sity of spark. This well-known dark space appears to 

 be a layer of molecular disturbance identical with the 

 invisible layer of molecular pressure or stress, the inves- 

 tigation of which has occupied the exhibitor some years. 



2. The Electrical Radiometer. — An ordinary radiometer 

 is furnished with aluminium cups for vanes. The fly is 

 supported by a hard steel cup, and the needle point on 

 which it works is connected with a platinum terminal 

 sealed into the glass. At the top of the radiometer bulb 

 a second terminal is sealed in ; the radiometer can there- 

 fore be connected with an induction coil, the movable fly 

 being made the negative pole. At low exhaustions a vel- 

 vety violet halo forms over each side of the cup. On 

 increasing the exhaustion the dark space widens out, 

 retaining almost exactly the shape of the cup ; the bright 

 margin of the dark space becomes concentrated at the 

 concave side of the cup to a luminous focus, and widens 

 out at the convex side. On further exhaustion, the dark 

 space on the convex side touches the glass, when positive 

 rotation takes place. 



3. Green Phosphorescent Light of Molecular Impact. — 

 At very high exhaustions the dark space becomes so large 

 that it fills the tube, and when German glass is used the 

 sides are beautifully illuminated with a greenish yellow 

 phosphorescent light. 



4. Projection of Molecular Shadows. — The rays excit- 

 ing this green phosphoresence will not turn a corner in 

 the slightest degree, but radiate from the negative pole in 

 straight lines, casting strong and sharply-defined shadows 

 from objects which happen to be in their path. The best 

 and sharpest shadows are cast by flat disks, and not by 

 narrow pointed poles ; no green light is seen in the 

 shadow itself, no matter how thin, or whatever may be 

 the substance from which it is thrown. 



5. Magnetic Deflection of the Trajectory of Molecules.— 

 The stream of molecules, whose impact on the glass is 

 accompanied by evolution of light, is very sensitive to 

 magnetic influence, and the shadow can be deflected by 

 bringing a small permament magnet near, the amount of 

 deflection of the stream of molecules being in proportion 

 to the magnetic power employed. The trajectory of the 

 molecules forming the shadow is curved when under 

 magnetic influence. 



6. Focus of Heat of Molecular Impact. — Great heat is 

 evolved when thfe concentrated focus of molecular rays 

 from a nearly hemispherical aluminium cup is allowed to 



fall on a strip of platinum-foil, the heat sometimes ex- 

 ceeding the melting-point of platinum. 



7. Mechanical Action of Projected Molecules. — An 

 actual material blow is given by the impinging molecules. 

 A small vaned wheel bemg used as an indicator, by ap- 

 propriate means the molecular shadow of an aluminium 

 plate is projected on the vanes. When entirely in the 

 shadow the indicator does not move, but when the mole- 

 cular stream is deflected so that one-half of the wheel 

 is exposed to molecular impact it rotates with extreme 

 velocity. 



8. Phosphor ogenic Properties of the Molecular Stream. 

 —Substances known to be phosphorescent under ordinary 

 circumstances shine with great splendour when subjected 

 to the negative discharge in a high vacuum. («.) Becque- 

 rel's Luminous Sulphide of Calcium shines with a bright 

 blue-violet light, and when on a surface of several square 

 inches, is sufficient to faintly light a room, {b.) The 

 Diamond is very phophorescent. Most diamonds from 

 South Africa phosphoresce with a blue light. Diamonds 

 from other localities shine with different colours, such as 

 bright blue, apricot, pale blue, red, yellowish green, 

 orange, and pale green. One large fluorescent diamond 

 gives almost as much light as a candle when phosphor- 

 escing in a good vacuum, (c.) The Ruby glows with a 

 rich full red, and it is of little consequence what degree 

 of colour the stone possesses naturally, the colour of the 

 phosphorescence is nearly the same in all cases. 



Besides these experiments the working of the writing 

 telegraph, exhibited by Mr. E. A. Cowper, attracted much 

 interest. The nature of this invention we described when 

 it was first announced, and gave a specimen of the kind 

 of writing produced. Other exhibits deserving notice 

 were Prof. Guthrie' s broken glass in frames, illustrating 

 the fracture of colloids, Edison's loud-speaking tele- 

 phone, Messrs. Preece and Stroh's synthetic curve 

 machine, and frame of curves produced thereby ; their auto- 

 matic phonograph, electromagnetic vowel-sounder, stereo- 

 scopic curves, synthetic sounder and syren, and phonauto- 

 graph. Apparatus and instruments of various kinds were 

 also exhibited by Messrs. Browning, Hilger, and Tisley 

 and Co. Among Mr. Hilger's exhibits was a quartz spec- 

 troscope for the ultra-violet rays, constructed for the 

 Scientific Society of Stettin, under the direction of Dr. 

 Schonn. 



A NEW CALENDAR CLOCK 



T T has always been a matter of surprise that the Ameri- 

 •*• cans can produce their well-known eight-day clocks 

 in such large quantities, so uniformly good for ordinary 

 purposes, and at such very moderate cost. Their general 

 efficiency is proved by the increasing demand for them ; 

 not only are they sold in the American made cases, but 

 separate movements are extensively imported and cased 

 in England. One of the largest firms by which they are 

 produced, that of Seth Thomas and Co., at Thomaston, 

 Conn., has recently introduced a hbrary or office clock 

 of very moderate cost, one form of which is shown in the 

 accompanying figure. This consists of the ordinary 

 eight-day striking movement supplemented by an in- 

 teresting and ingenious mechanism for operating the 

 calendar ; by its means not only the month and day of the 

 week and month are indicated as in ordinary calendars, 

 but the several months have their allotted number of 

 days, an additional day being given to February in leap- 

 year. Of course contrivances for effecting this object 

 have long been known, but they always add so materially 

 to the cost that they are prevented from coming into 

 general use. 



It would be impossible to fully explain the mechanism 

 employed without the aid of drawings ; a general descrip- 

 tion must therefore suffice. As will be seen, the calendar 

 dial is placed below the clock dial, and is divided on its 



