November 30, 1893] 



NATURE 



105 



November 6, he glimpsed the spot in its entirety, and 

 describes it as of a pinkish colour. The following and 

 south following part of the spot had quite a dark and 

 definite outline. 



On October 31 the red spot was seen with the 16-inch 

 refractor at the Goodsell Observatory, Northfield, U.S.A. 

 It was not a difficult object, though the colour is stated 

 as being very faint. " The S. side of the spot and a belt 

 of similar tint appeared to merge into one another 

 without the slightest change in intensity of colour." 



On November 23 I observed the spot with an 8^-inch 

 reflector belonging to my friend, Mr. J. Harvey Jones, 

 of Bristol ; but the night was not very good. The red 

 spot was faintly seen, and must have been central at 

 about iih. 25m. Other details were also noticed as 

 follows : — 



A faint, narrow, dark belt, like an irregular pencil-line, 

 on the equator. A similar belt running from about the 

 p. end of the red spot to W. limb of the planet. The 

 shouldering of the S. equatorial belt N. of the ends of the 

 red spot was distinctly seen, though that part N. of the 

 p. end was very faint. The f. shoulder shows a much 

 more gentle slope than formerly. Numerous reddish 

 spots were seen on the N. side of the N. equatorial belt. 

 These were large and conspicuous, as were a series of 

 bright spots p. and S. of the red spot. A remarkably 

 brilliant spot on the N. side of N. equatorial belt was 

 central at loh. exactly. 



The general appearance of the planet betokened a 

 more disturbed condition than usual, the belts being full 

 of irregularities. 



The great size, durableness, and special character of 

 the red spot have naturally attracted much discussion, 

 and a number of theories have been broached to explain 

 the nature of the spot, and to account for its long endu- 

 rance. Some writers have regarded it as part of the 

 solid material of Jupiter, but this theory is practically 

 negatived by the fact that it has shown an irregularity 

 of motion. Unless we admit that the rotation period of 

 Jupiter is extremely variable, and has experienced con- 

 siderable retardation in recent years, we cannot allow 

 that the red spot forms a portion of the sphere. Others 

 believe the spot to represent a condensation of material 

 floating or suspended above the surface of the planet, and 

 that variations of motion and tint are impressed upon it 

 by the action of the Jovian atmosphere, which is con- 

 stantly in a state of turmoil. Another idea has been 

 mooted to the effect that the spot may possibly be an 

 opening in the atmosphere, through which the surface of 

 Jupiter has been exposed, and that the recent feebleness 

 of the object is occasioned by the filling in of the cavity 

 with highly reflective vapours. 



The Rev. E. Ledger remarks that at one time he felt 

 inclined to believe that the permanency of the spot 

 "seemed to indicate that it might be something which, 

 while coagulating or solidifying, in some way caused a 

 gap or break in the cloudy regions above it, or by its 

 cooling condensed the vapours incumbent upon it, and 

 thus increased its own visibility ; in fact, that we might 

 be watching in it the gradual formation of a huge con- 

 tinent upon Jupiter." 



The theory has also been advanced that the spot 

 was originally formed by ejecta from a volcanic region 

 immediately underlying it, but it must be admitted that 

 no hypothesis appears to be entirely satisfactory in its 

 application, and certainly we cannot regard any one of 

 them as capable of being definitely proved. In a word, 

 it must be avowed that though we have become familiar 

 with the red spot, its motion, shape, and variable tints, 

 during observation extending over more than fifteen 

 years, we are yet far from, understanding the mystery it 

 involves. Its production was doubtless the outcome of 

 the energy and activity prevailing above, and possibly on, 

 the planet's surface, but in what particular way the spot 



NO. 1257, VOL. 49] 



was generated it is impossible to say. Nor is the specific 

 date of its first apparition known ; it may be a modern 

 resuscitation of the spot which delighted Hooke and 

 Cassini about two centuries ago, or it may only have been 

 initiated into existence just before those memorable 

 nights in July, 1878, when it exhibited an intensely red 

 colour, and struck observers, instantly, as being a most 

 anomalous feature. 



But though the spot forms an unsolved mystery, it will 

 continue to be watched with interest by telescopic ob- 

 servers, who will much regret if its present faintness is 

 but the prelude to final dissolution. It can be justly said 

 that no planetary marking visible in modern times has 

 encouraged as much observation, and incited the same 

 amount of interest as the familiar " red spot on Jupiter." 

 Possibly the further study of this remarkable formation 

 may yet enhance our knowledge of the physical condition 

 of the "giant planet," and throw some light upon the 

 singular variations so rife upon his expansive surface. 



W. F. Denning. 



THE PREPARATION AND PROPERTIES OF 

 FREE HYDROXYLAMINE. 



A CONSIDERABLY improved method of isolating 

 -^"^ hydroxylamine is described by Prof. Briihl, of 

 Heidelberg, in the current Berichte, by which a tolerably 

 large quantity of the pure substance may be prepared 

 without danger in a short space of time, and which may 

 therefore be of general interest on account of its suit- 

 ability for lecture and demonstration purposes. It may be 

 remembered that M. Lobry de Bruyn, who first isolated 

 solid hydroxylamine two years ago {znde Nature, vol. 

 xlv. p. 20), prepared it from a mixed solution of the 

 hydrochloride and of sodium methylate in methyl alcohol. 

 This solution, after removal of the precipitated common 

 salt, was first concentrated over a water bath, under the 

 diminished pressure of 100 m.m.,and afterwards subjected 

 to fractional distillation over a flame at the still lower 

 pressure of 40 m.m. A continuous fractionating vacuum- 

 apparatus was considered unsuitable, and the change of 

 receivers could only be conveniently effected by tem- 

 porarily arresting the distillation. This mode of operating 

 frequently led to violent explosive decomposition of the 

 heated hydroxylamine, and, moreover, the yield rarely 

 exceeded 17 per cent, of the theoretical. Prof. Briihl, 

 desiring to obtain a considerable quantity of the pure base 

 for spectrometric purposes, has been led to devise the 

 following much more convenient method : — 



The methyl alcohol solution is first separated from the 

 precipitated salt, and then immediately transferred to a 

 slightly modified form of the well-known apparatus of 

 Prof. Briihl for fractional distillation in vacuo. This 

 apparatus consists essentially of a distilling flask, pro- 

 vided with thermometer and entrance tube furnished 

 with tap, a condenser, and a receiving arrangement which 

 provides for the repeated and rapid change of receiver 

 without impairing the vacuum and without arresting the 

 distillation. This receiving arrangement consists of a 

 short but wide cylinder of stout glass, into which the end 

 of the condensing tube is introduced through a tubulus 

 fitted with bored caoutchouc stopper ; inside the cylinder 

 is a circular stand carrying six receiving tubes, which are 

 capable of rotation by means of a rod passing, gas-tight, 

 through a tubulus and its caoutchouc stopper in the top 

 of the cylinder, and terminating in a handle outside. By 

 suitable manipulation of the handle, each of the six 

 receivers may be brought beneath the end of the con- 

 densing tube in turn while the distillation is proceeding. 

 The distillation of the methyl alcohol solution contained 

 in the distilling flask is effected by reducing the pressure 

 to the lowest possible amount, and supplying the necessary 

 heat by immersing the flask in a bath of hot water. On 



