yan. 25, 1872] 



NATURE 



243 



Condurango 



I HAVE read in No. 104 (October 26, 1 871) of your scientific 

 and higlily-interesnng joumil, a few words on "Condurango," 

 the new Ecuadorian plant that has lately called so much general 

 attention in Europe and America to its supposed properties ol 

 curing cancer. 



The want of exactitude in the description of the plant w U 

 doubt le-^s give an erroneous idea of it to your readers, and with 

 tlie desire of eff icing such errors as tho-ie publishei in the 

 "Andes" of Guayaquil, and in Bogo'a by Mr. Buyon, to 

 whom you make reference, allow me to present to you and your 

 readers the bo'anical description of the Condurango twining 

 plant, verv useful, indeed, in some rheumatisms and secondary 

 syphilitic disorders, but of very doubtful medicinal properties in 

 cancer, so far as my own evpenence goes. 



The Condurango belongs to \h& orier Asclepiadacei^. 3rd tribe, 

 which corresponds to Aclcpia ies vera ; 1st div sion Astephaniis, 

 whose characters are that the li.nb of the corolla is without 

 scales, and the stamens without appendage or cirona. 



This division comprehends only five genera, viz., Alitostigma^ 

 Astephanus, Hicvmx, Hcinipogon, and Nanlonia. In none of 

 these genera can the Condurango be classed. 



The genus Mitostigma, as a distinguishing character, has two 

 long filaments at the end of the stigma, and this is not the case 

 in Condurango. The genus Astephanus has the sepals acute, the 

 corolla subcampanulate, and the stigma elongated ; chiracters 

 that do not belong to the Condurango. The genus ffamax has 

 the divisions of the corolla hooded, and other characters not 

 observed in the Condurango. The genus IPcniipogoii has the 

 sepals of the caly.\ acute, hard, and with a curved extremity. 

 The corolla is campanulate, which is not the case in Con- 

 durango. The genus Nantonia has the sepals striated and 

 curved, which also is not the case in Condurango. 



The flowers of the Condurango have a calyx of five division>, 

 obtuse, ovate, and vido^e in their inferior part, and of quin- 

 cuncial prjeflorescence. The corolla is rotate, of five divisions, 

 lanceolate, hairy at the base on the inside, and somewhat fleshy, 

 with a membranous margin. Its aestivation is imbricarei. The 

 stamen has no appendage or corona ; the anthers are terminated 

 by a membrane, and the poUen mrsses are elongated and sus- 

 pended. The stigma is pentagonal and conical. The flowers 

 are numerous and disposed in umbelliferous inflorescence. 



As afiresaid, the Condurango forms a new genus. It is absurd 

 to speak of Condurango as it it were the same as Mikania hiiaco. 



In the importance of the subject I hop.e to find ample apjlogy 

 for asking room in your columns for these few lines. 



A. Destruge 



Guayaquil, Ecuador, Dec. 13, 1871 



Ocean Currents 



It appears to me that the numerical data adduced by Mr. 

 Croll in his letter (Nature, Jan. 11) disprove his conclusions. 



The doing of 9 foot pounds of work upon a pound of water 

 should give it a velocity (in feet per second) of 



\/2 X 32 X 9 = 24 ; 



and the doing of one foot-pound of work upon a pound of water 

 should give it a velociiy of eight feet per second. These are 

 much greater than the observed velocities, so that a margin is 

 left for friction. 



The following passage in Mr. CroU's letter also calls for some 

 remark: — "But it mu..t be borne in mind that the deflecting 

 power of rotation depends wholly on the rate at which the body 

 is moving. If difference of specific gravity be regarded as the 

 impelling cause of any current, the deflecting power of rotation 

 will certainly be infinitesimal." 



The deflecting force does indeed vary directly as the velocity 

 of the body acted on ; but the curvature of path which the de- 

 flecting force tends to pioduce, is proportion.il to the quo'.ient 

 of the deflecting force by the square of the velocity, and there- 

 fore v?ries inversely as the velocity. In latitude 45°, a velocity of 

 a foot per second would give a radius of curvature of less than 

 two miles. Here, then, again, there is a wide margin left for 

 resistance. The expression for the radius of curvature in feet, 

 supposing that there are no resistances, is 

 6S50P 

 sin K 

 A being the latitude, and v the velocity in feet per second. 



Belfast, Jan. 13 J. D. Everett 



Mock Sun 



I THUS name the phenom -non I am about to describe, but 

 wi hout regard to scientific accuracy. List evening, a little be- 

 fore sunset, I observed a dark bink of clouds couched on the 

 horizon, just beneath the sun, and a long miss of cirro-stratus 

 above him. A band of light, of about half his width, stretched 

 up and down to the c ouds. This renainei visible, with remidc- 

 able changes, till 25niin. af er the sun's total immersion. On his 

 disappearance the band gradually widmed (or seemed to di> so), 

 and assumed the f)n"n of a table flower- vase, i e,, bulged a: the 

 base and cylndrical above. At ten minutes after sund >wn the 

 band, wnich hai been about 10° in lenitii, stretched to 20°, being 

 superposed on the cirro-stratus, where it was rose-cojoured, the 

 bulged portion being orange. At twenty minutes after sun- 

 do.vn a slight co lipse occurred, and the band almjst dis- 

 appeared, the bulged pirtion becoming an orange disc, just like 

 a second sun setting in fog. Soon afterwards this became elon- 

 gated, and the band reappeared, stretching over an arc of 40^ 

 A few minutes liter all rlisippeareJ. I witnessed this beautiful 

 pheno'iienon from a c irriage on the L. and N. W. Railway, on 

 both sides of Blisworth. C. M. Ingleby 



Edgbaston, Jan. 20 



Solar Eruptions and Magnetic Storms 



At a recent meeting of the Astronomical Society a paper was 

 read by Mr. Ranyard, in which sjme suggestions were put for- 

 ward concerning the possibdity of accounting for the solar pro- 

 minences on the supposition that they may be caused by the 

 projection of matter from a lo-ver level, and that such an up- 

 rush into and through the layers above, emerging into the lighter 

 envelope of the chromosphere, might lift before it a cone of com- 

 pression of the ga-eous matter, producing an elevation on the 

 surface, visible to us as a prominence. And the solid particles 

 or masses thus projected miglt form meteorites, the shape 01 the 

 prominence being afterivards modified by other causes. 



This thcoy, offering as it does a pos-.ijle account of the genesis 

 of prominences and meteorites, appears to contain the germ of 

 another hypothesis respecting the ciuse of the connection be- 

 tween sola' eruption ani terrestrial magnetism. 



If it be legitimate to suppose that in and near the photosphere 

 we have a circuit ot conducting matter (viz. incandescent me- 

 tallic vapours), ace irding to well-known facts any cruse tend- 

 ing to effect an unequil distribution of heat, and at the same 

 time a want of homogeneity of structure, such as a difference of 

 pressure or density, would establish thermo-electric currents in 

 such a circuit. 



Now such a difference would arise from an upward burst of 

 matter from below the photosphere. If, therefore, the pr.imi- 

 nences have their orig n at great depths below the photosphere, 

 we may expect currents of considerable inten-ity to circulate 

 round the equatorial region of the sun. In the equatorial legion 

 rather than in any other, because it is there that the greatest dis- 

 turbance is manifested, as shiwn by observations on the limits 

 of spo s and prominences ; and, therefore, there that the neces- 

 sary differences of temperature a e most lik-ly to occur, the 

 effects of such currents being to crea'e secondary or reduced 

 currents in the adjacent layers, and, if of sulficient intensity, in 

 the earlh itself. 



Provided that this be so, this supposition will suffice to recon- 

 cile some observed facts. Secchi has deduced,* in treating of 

 the periodical variations of the magnetic elemen.s, the law that 

 " The annual disturbances are at a maximum at the equinoxes, 

 and at a minimum at the solstices." 



Knowing then that the plane of the sun's equator passes 

 through the earth on June nth and Dec. 12th, and that there- 

 fore tue equator as set-n from the earth presents its widest ellipse 

 in March and Septemb. r, it follows that such thermo-electric 

 currents, if tney exist, are able to exert their maximuiu inductive 

 effect on he earth at or near the equinoxes. 



The case is analogous 10 the experiment in which terrestrial 

 magnetism is made to cause induced currents in a closed circuit 

 rotated round an axis at right angles to the nugnetic meridian. 



In this case the ring is placed successively in positions 

 various y inclined, but always keeps its plane perpenJieular to 

 the meridian, and ttie maximum indueed cun'enc then occurs. 



Similarly, soUr equatorial currents would produec their maxi- 

 mum effect wnea the plane of the sun's equator has its aspect 

 most nearly in the direciion of the earth, and although any 



• De La Rive's Electricity, torn. iii. p. 780. 



