Nov. 13, 1879] 



NATURE 



35 



A COCHIN-CHINA REMEDY FOR LEPROSY 



A NOTE in NATURE (vol. xxi. p. 19) refers to a remedy 

 for leprosy, obtained from Cochin-China, but the 

 origin of which is imperfectly known. Its name is given 

 as hwang-nao. In Mr. Consul Tremlett's Report (For. 

 Off. Repts. No. 21, p. 1237) it appears as hoang-nan. 

 We have taken a good deal of trouble about this drug at 

 Kew, and the inclosed extract from the Kew Report for 

 1877, p. 31, contains all that has been positively ascer- 

 tained about it at present : — 



" Hodng-nan, a Supposed Remedy for Leprosy. — Mr. 

 Prestoe, Superintendent of the Trinidad Botanic Garden, 

 has drawn my attention to some accounts given in Lcs 

 Missions Caiholiques for 1875, describing the surprising 

 efficacy of a drug, the produce of a plant found in Cochin- 

 China, in the treatment of leprosy and rabies. The plant 

 is known by the name of Hoang-nan, and the description, 

 which is of the vaguest kind, represents it as a climber, 

 and its bark as the efficacious portion. 



" M. L. Pierre, the Director of the Botanic Garden at 

 Saigon, has obtained an imperfect specimen of the 

 Hoang-nan, and informs me that he identifies it as a new 

 species of Strychnos, which he has named .£ gaulheriana, 

 in honour of the ecclesiastic who first gave the virtues of 

 the Hoang-nan a wider publicity. 



" M. Pierre adds some remarks which appear to me 

 worthy of placing on record: — 'The bark of Strychnos 

 nux-votnica is regarded in Cambodia and Siam as a 

 poison no less certain than that extracted from the seeds. 

 The natives have remarked the fact, which is also believed 

 to hold good in the case of cinchonas, that the bark has 

 the most powerful properties when it has been covered 

 with moss or otherwise protected from the action of light.' 

 In collecting the bark great attention is paid in conse- 

 quence to the circumstances under which it has been 

 produced." W. T. Thiselton Dyer 



SOME POINTS IN THE HISTORY OF 

 SPECTRUM ANALYSIS 1 

 A PHYSICAL problem begins like a rivulet. At its 

 ■**■ first introduction it is small and seemingly unimpor- 

 tant — constantly however, as it winds along it receives 

 accessions from various quarters until at length it becomes 

 a mighty river that is finally merged in the unfathomable 

 ocean. This course is followed by all such problems. 

 Each begins small— grows broader and will finally bear 

 us on to the unknown if we trust ourselves to its guid- 

 ance. 



I need hardly remind you that the demonstration of 

 the decomposition of white light was one of the triumphs 

 of the illustrious Newton. But like other problems it had 

 its small beginning. We find in one of the earliest me- 

 moirs of the Royal Society, a paper on " The Genuine 

 Method of Examining the Theory of Light and Colours," 

 by Mr. Newton. Here he asks amongst others, the 

 following questions : — 



(1) Whether rays that are alike incident on the same 

 medium, have unequal refractions ? 



(2) Whether rays endued with particular degrees of 

 refrangibility, when by any means separated, have 

 particular colours constantly belonging to them, viz., the 

 least refrangible scarlet, the most refrangible deep 

 violet, the middle sea green ; and others other colours ? 



(3) Whether colours by coalescing do really change 

 one another to produce a new colour, or produce it by 

 mixing only ? 



(4) Whether a due mixture of rays, endued with all 

 variety of colours, produces light perfectly like that of the 

 sun ? and he ends by remarking that the most proper and 

 direct way to a conclusion is to determine such queries by 



' Bring an address delivered by Dr. IS. Stewart, F.R.S., at the opening 

 of the present session, to the Natural Philosophy Classes at Owens College. 



experiment. Then follow some objections to the theory 

 of light and colour, by the Rev. F. Pardies and Mr. 

 Newton's reply to these objections. Into the nature of 

 these however, it is not my purpose to enter. Let me 

 rather adopt Newton's suggestion and bring the experi- 

 ment itself before you. 



You are all, no doubt, familiar with the operations of 

 the photographer, and as a matter of fact you know that 

 when the light from a natural object is made to pass 

 through his lens an image of this object is impressed 

 upon the sensitive plate placed at the focus at the other 

 side of the lens. 



If the natural object be a friend's face you obtain 

 his photograph, if it be a tree, you get the image of the 

 tree, if it should be a bright slit of light or a bright wire 

 you would get the image of the slit of light or of the wire. 

 Now here we have a slit which is rendered luminous by 

 an intense light thrown upon it, and if we place a photo- 

 grapher's lens before it we shall obtain an image of the 

 slit. You see the image thrown upon a screen and you see 

 moreover that the light is white ; it is in fact the electric 

 light which illumines the slit. For the machine by which 

 this light is produced our college is indebted to the gener- 

 osity of Mr. Wilde. But my object is not now to discuss 

 the electric light, but to show you that it is white and 

 like the light of the sun — since, as you see, its image on 

 the screen is white. Let us now interpose a prism or 

 train of prisms between the lens and the screen. These 

 prisms will do two things. In the first place they will 

 bend the rays towards the base or thick part of the 

 prisms so that in order to catch the image the screen 

 must be moved in this direction. But in the second place 

 they will bend some rays more than others ; — if the slit be 

 lighted by pure red light it will be least bent, if by orange, 

 this will be more bent than the red, if by yellow this will 

 be more bent than the orange, then follow green, blue, 

 indigo, and violet, the latter of which is most bent. 



Now if the light behind the slit be a mixture of red, 

 orange, yellow, green, blue, indigo, violet, we shall have 

 a series of images of the slit overlapping one another, and 

 forming a long ribbon of light of which the portion least 

 bent will be coloured red and that which is most bent 

 will be violet. Let us now see what we get from the 

 light we are using. Here you see we have all the colours 

 of the rainbow, red, orange, yellow, green, blue, indigo, 

 violet, and therefore our light must contain all these ; but 

 our light was white like that of the sun and thus you see we 

 are entitled to say that white light is composed of a 

 mixture of these various colours. 



In fact what we have done by the prism has been to 

 separate these various constituent rays from one another 

 and throw one on one part of the screen and the other on 

 another part. But now if we make these various con- 

 stituents to dance so quickly before our eyes that we get 

 a united impression of the whole, we shall imagine once 

 more that we have white light. We separated the rays 

 in space — let us now combine them in time — and you see 

 the thing is white. We have thus demonstrated the com- 

 position of white light after the way by which the chemist 

 proves the composition of water, first decomposing it by 

 the battery into oxygen and hydrogen, and then causing 

 these two gases once more to recombine. I will now 

 remind you that light consists of waves or undulations 

 given out by the luminous body. These waves take place 

 in a medium called ether, surrounding us all, in which 

 they proceed with incredible swiftness. The light given 

 out by a luminous particle may thus be compared to the 

 note or notes given out by a bell. In solids and liquids 

 however the particles are so closely packed together 

 that they may be likened to a number of different bells 

 all tied together in such a way that the total mass is 

 capable of giving out every, or almost every, variety of 

 note. From an incandescent solid or liquid body, when 

 sufficiently hot, you thus get every variety of light, and 



