Dec. 23, 1886J 



NATURE 



175 



The figures given of these particles show that they 

 closely resemble pumiceous dusts (see Nature, vol. xxix. 

 p. 5S7). An examination of the sandstones with which 

 these dusts are sometimes found interstratified proved 

 that they consist of well-rounded particles of triclinic 

 feldspar, hornblende, and magnetite, and that they are 

 therefore, like the associated dust deposits, of volcanic 

 origin. 



Among a series of so-called " Pliocene sandstones " 

 collected in Montana and Idaho in 1S71 by Dr. A. C. 

 Peale, of the Hayden Survey, Prof. Merrill was able to 

 detect similar pumiceous sands in a more or less pure 

 state. In their microscopic characters several of these 

 were found to be very similar to the pumice-dust which 

 was thrown out so abundantly during the great eruption 

 of Krakatab. 



" All of the above-mentioned dusts yielded water when 

 heated in a closed tube, and fused readily, with swelling, 

 before the blow-pipe. Samples submitted to Mr. J. E. 

 Whitfield, of the Geological Survey, for analysis, yielded 

 results as follows : — 



99-92 



100-74 



99-66 



Accepting the apparently well-founded conclusions of 

 others to the effect that such dusts represent the extreme 

 degrees of acidity of the lavas of which they formed a 

 part, we are led to consider these as of andesitic or possibly 

 trachytic derivation." 



Other similar materials have been examined from 

 Bridger Creek, on summit of a hill near Bozeman, and in 

 connection with fossil bones from the Niobara Loup Fork 

 and Sweetwater regions, A sample obtained from the 

 base of the Mazatzol Mountains at the edge of Verde 

 River V'alley is stated to be quite similar to that described 

 from the east of the Black Hills of Dakota, described by 

 Dr. Wadsworth,'- and also to those previously described 

 by Prof. Merrill from Nebraska. Cither similar dusts have 

 been obtained by the officers of the United States Geo- 

 logical Survey from Wray Station in Eastern Colorado, 

 and from Norton and Phillips Counties, Kansas. 



" In studying the probable origin or sources of these 

 various beds, the distances which the dust can be carried 

 by atmospheric currents is likely to prove of importance. 

 It may therefore not be out of place to state here, that 

 among a collection of pumices, ashes, &c., from the 

 Krakatab eruption in 1883, and which were donated to 

 the Museum by T. H. Houghton, was a small sample of 

 the dust (36974) that ' showered on board ship Beacoiis- 

 Jield at the rate of one inch per hour for three days, in 

 latitude 14° S., longitude 92" E., or at a distance of 855 

 miles from the scene' of volcanic activity. This dust is 

 a very pure, nearly colourless, gray and highly pumiceous 

 glass, the particles of which vary in size all the way up 

 to 0-25 mm. 



" As a matter of economic interest I may say in con- 

 clusion that in Kansas and Nebraska these dusts are 

 collected and sold in paper packages as ' diamond polish- 

 ing-powder,' or put into soap which is sold for general 

 scouring as well as for dental use under the name of 

 ' Geyserite soap.' " 



' Water given off a 

 2 Science, July 24, 



05' C. 



THE POTATO TERCENTENARY 

 A N article on "The Origin ofour Potato," which appeared 

 ■^*- in our columns on May 6, contained these words : 

 " It would be a fitting observance of the third centenary 

 ... if we could celebrate it, not by speeches and after- 

 dinner toasts to the memory of Drake or of Ralegh, but 

 by clearly laying down our lines of inquiry, for they have 

 been very ill-defined." These words, penned by our con- 

 tributor with then no definite idea as to the way in which 

 various thinkers could be brought together to help to lay 

 down lines of inquiry, have bad their eflect. The pro- 

 prietors of the St. Stephen's Hall took the subject up, and 

 in a circular headed 1586- 1886, printed in old English 

 type, referred to the article in N.\ture as drawing atten- 

 tion to the fact that 1886 was the accepted date for the 

 tercentenary, and amrouncing their intention to celebrate 

 it in the spirit suggested, with Conferences and an historic 

 and scientific Exhibition, conjoined with a display of all 

 known varieties of tubers that could be obtained. A 

 " Scientific Committee of Consultation " readily oflered 

 their services to arrange the " historic and scientific " 

 portions of the Exhibition and to conduct the Conferences. 

 Leaving, as it was seen we were, the old lines of cultiva- 

 tion, and entering on a more thoughtful, a more scientific 

 way of procedure, the turning-point appeared to demand 

 a recognition of the past, an exposition of present know- 

 ledge, and something tangible of the on-look into the 

 future. 



The proprietors of the St. Stephen's Hall, while 

 acting as the executive, and arranging the display of 

 tubers, and otfering gold, silver, and bronze medals, left 

 all the scientific work to the Committee of Consultation. 

 Those who first accepted their responsibilities had to 

 seek the co-operation of others, and only those who were 

 specialists in the portion of the subject they represented 

 were invited to join it. In the list of sections as drawn 

 up, the botanical aspects of the question naturally came 

 first, and Mr. J. G Baker, F.R.S., of Kew, undertook 

 to illustrate " The Known Wild Species of Solanum," 

 which he did partly by dried specimens and partly by 

 drawings. No one was found to undertake the section 

 " Batatas, yams, ighnamas, &c., that in Elizabethan 

 times were called potatoes," but specimens of yams and 

 so-called batatas were shown. .Some uncertainty about 

 the vernacular nomenclature of these seems to exist. The 

 section "Cultivation by the Incas and other Andean Na- 

 tions " was accepted by Mr. C. R. Markham, C.B., F.R.S., 

 who in the Conference added more information than could 

 be given in the form of an exhibit. For the next section on 

 the programme, ''Early Cultivation in the British Isles," 

 no one could be found. This is a fact worth notice. 

 There must sui-ely be some one who has paid attention 

 to this subject, yet even after the Committee was fully 

 formed it was not known to whom to apply for information. 

 The next section, " Cultivation," with its sub-sections 

 — (i) Selection, (2) Cross-breeding, (3) Hybridisation, 

 (4) Grafting — was undertaken by Dr. Alaxwell Masters, 

 F.R.S. ; and the following section, "Potato-disease," 

 was well filled up with contributions from Mr. W. Car- 

 ruthers, P.L.S., Mr. Worthington Smith, Dr. Plowright 

 and Mr. Geo. Murray, F.L.S. For the section " Chemistry 

 of the potato and batata as a food " Prof. Church sent 

 new analyses, and Mr. \V. Topley, F.G.S., of the Survey, 

 contributed maps and notes on " Soils suitable for Potatoes 

 geologically considered." 



In " Meteorology as affecting Disease," Mr. J. G. 

 Symons, F.R.S , exhibited rainfall maps showing coinci- 

 dence with special disease years. The next section, 

 " Historic literature of the potato," was in charge of Mr. 

 W. S. Mitchell, M.A., and by the help of dealers in old 

 books, and of private collectors, the list he had drawn up 

 had but one gap — a Monardes. Such a collection has no 

 before been brought together. The section " Maps show'ng 

 the knowledge of the New World at the time of Elizabeth " 



