158 



KNO^ATLEDGE 



[May 1, 1888. 



NEVADA'S WALTZING GIANTS. 



||UT in Nevada," said a mining man from 



White Pine, " we liave the sublimest dance 



that any man ever saw. We call it ' the 



dance of the giants.' Great cylinders of 



iK'^Wi^'^jRI ^^^^t from eight to twenty feet in diameter, 



iiY^B ^aMll ^^'^ sometimes immensely tall, come 



' ' cai'eering acro.ss the desert with a whirling, 



waltzing motion that is very graceful. I have often seen 

 them when they must have been two or three miles high, 

 for their tops reached into the clouds. But oftener there 

 will be one big column, with a lot of little columns attend- 

 ing it, all waltzing together. The eflFect is the strangest 

 thing imaginable. It is both sublime and grotesque. It 

 inspires you with awe, and at the .same time fills you with 

 the desire to laugh at the odd performance. And, if the 

 man is superstitious, the weird, fantastic sight can make 

 him I'eel mighty uncomfortable. 



" They are never seen except in the summer time, and are 

 most frequent in July. They have their beginning in some 

 incipient whirlwind, which snatches up a handful of sand 

 while the surrounding air is still, and then they keep on 

 growing and moving onward. 



" They are not like the cyclones farther east, ibr they 

 move with very little noise, and, instead of being funnel- 

 shaped, are of the same size from toji to bottom. The motion 

 is the same, being both circular and advancing. They draw 

 up into the cylinder fabulous quantities of sand, tons of 

 sage-brush, and sometimes good-sized stones. 



" How far they travel nobody can tell. The very big ones 

 must have waltzed along in their silent majesty over the 

 lonely deserts for a long distance. They must travel the 

 whole distance of the White Pine Valley, three hundred 

 and fifty miles, and .sometimes they come down through 

 Spring Valley from Idaho to the Peranegat Valley." 



THE STARS OF OTHER TIMES. 



DO not think I am a very lazy man ; and in 

 regard to mapping and charting, I think — 

 though it may be sheer self-conceit — that I 

 have at times been exceptionally hard-working. 

 Probably not many thousands, or even hun- 

 dreds, or tens of persons have given so much as 

 400 hours to a single map — possibly not one 

 besides myself (unless I be thought somewhat beside 

 myself to have undertaken such a work). Therefore I am 

 not ashamed to explain the devices by which, when I can, T 

 simplify the work of charting. I will go further. I regard 

 the use of easy methods, when these are sufficiently accurate 

 for the object aimed at, as akin to the use of those abridged 

 processes of calculation by which the mathematician who 

 has sufficient experience to work confidently in such ways, 

 leaves out all such portions of the ordinary processes as are 

 not essential. The average calculator will multiply and 

 divide right out, extract his square roots and cube roots to 

 the bitter end, take out every logarithm to the seventh 

 figure, and determine, with like accuracy, the numbers 

 corresponding to his logarithm, when all he needs (nay, 

 perhaps, all he can at all trust) in his results may be three 

 or four significant figures. This really is not accuracy ; it 

 is blundering : it is the result not of scientific care but of 

 inexperience, very often in the weariness resulting from over 

 precision of process the calculator makes mistakes seriously 

 aifecting the numbers finally deduced. In like manner, in 

 mapping there are many devices which not only save 



trouble but secure a greater accuracy than the preci.se 

 geometrical methods theoretically applicable to the problem. 



Such is the method which I am about to describe as the 

 one I have employed for preparing star maps showing the 

 heavens at given hours and seasons, in given latitudes, at 

 given epochs in the past history of the human race. 



Take Maps I. and II. in Knowledge for March and 

 April last. Having chosen an}' epoch and found the pole 

 for that epoch, on the circle indicating in each map the 

 pole's precessional path, it would be sufficiently easy to 

 describe in each map the circle indicating the diurnal track 

 of the zenith of the heavens around that pole for any given 

 latitude — for instance, a circle 60° from the pole for 

 the latitude of the Great Pyramid. It is also not difficult to 

 set points round a circle thus determined so that they shall 

 corres|)ond to hour-differences of time — that is, to divide the 

 circle into portions each representing 15° on the correspond- 

 ing circle of the sphere. To complete further the projec- 

 tions of the visible hemisphere corresponding to such points 

 as these for zenith points (i.e. centres of projection), is a suf- 

 ficiently simple piece of stereographic charting — theoreticalli/. 

 But all this work involves careful attention to the details of 

 the problem, some mathematical mental gymnastics, and 

 certain geometrical processes which require considei'able 

 care and some skill in the execution. Then, owing to the 

 unequal shrinkage of the paper, the results obtained by thus 

 describing circles according to the principles of the stereo- 

 graphic method, are not so accurate as they theoretically 

 ought to be. 



The following is the method I actually employ in such 

 work : — 



I lightly draw in pencil the courae of the circles of 

 declination and light ascension in my " School Star Atlas " 

 (dated 1880) among the longitude and latitude lines and 

 stars of Map I. I then ink them in strongly, correcting 

 while doing this the small irregularities affecting the light 

 pencilling. Next I make two tracings of these lines (really 

 circles and circular arcs) in red ink on tracing paper, one of 

 these to be used with Map I., the other with Map II. 



Suppose, now, that the epoch for which I want a series of 

 maps like my " Half-Hours with the Stars," for England 

 (latitude 51i° N.), or for the United States (lati- 

 tude 38° N.), or for the southern hemisphere (latitude 

 38° S.), is that of the building of the Great Pyramid — I 

 first find the right position of the poles for the year 3350 B.C., 

 and the corresponding crossing points of the equator of that 

 epoch on the ecliptic. (This, of course, requii-es only that 

 the right arc for 3.150-1-1,880 or 5,030 years' precession, 

 where the whole circuit requires 25,868 years, should be 

 taken on the ecliptic and on the pole's path.) Then these 

 three points being' marked, the prepared tracing papers are 

 adjusted — one over each map — so that the pole corre- 

 sponds with the polar point thus determined and the 

 equator crosses the ecliptic at the two marked points. 

 When the tracing papers are gummed at the edges or 

 corners in this position, the red circles and arcs are the 

 declination-parallels and hour-circles of the heavens, for the 

 epoch dealt with. 



Now to obtain maps presenting the stellar skies of any 

 latitude, we draw first on any projection we please (in my 

 " Half-Hours " and " Seasons Pictured," I use the equi- 

 distant) the hour circles and declination-parallels correspond- 

 ing to the latitude. This, of course, is a pi-ocess depending 

 on familiar principles of mapping [but I may take occasion 

 hereafter to show how it may be conveniently effected for 

 any projection, when once effected for the most convenient 

 projection — the stereographic]. Then, having made twelve 

 tracings (on drawing paper preferably) of this projection, 

 we fill in the stars for these from Maps I. and II., the red 



