456 



NA TURE 



[September 5, 1901 



above the surface on which it rests. But any abrupt change in 

 the slope of the surface near the gauge, whether it be an 

 embankment across a valley, a cliff, or a steep roof, or tower, 

 allows the wind to set up eddies, or acquire an increased 

 velocity, and so to reduce the amount of rain received in a 

 horizontal gauge." These principles are clear enough, and 

 they show the need for the adoption of a uniform height of 

 gauge by all members of the rainfall organisation. At present 

 it appears that not half the gauges in use are placed at exactly 

 the standard height. 



Messrs. Swan Sonnenschei.n and Co. have pub- 

 lished a third and revised edition of " Land and Fresh-water 

 Shells," by Mr. J. W. Williams, with a chapter on the distribu- 

 tion of the British land and fresh-water Mollusca, by Mr. J- W. 

 Taylor and Mr. W. Denison Roebuck. 



The additions to the Zoological Society's Gardens during the 

 past week include a ':>o':>V^ yi&n^aSity [Cercocehus fiiligitiosus) 

 from West Africa, presented by Mr. G. Nicholson ; a Rhesus 

 Monkey {Macacus rhesus, 9 ) from India, presented by Mr. J. 

 McCarthy; a Short-toed Eagle (Circaetus galiicus) from the 

 Atlas Mountains, presented by Captain W. R. Taylor ; a 

 Passerine Parrot {Psiltacnla passeriixa) from South America, 

 presented by Mr. W. C. Stronge ; two Turtle Doves (Tiirliir 

 coinmtinis), British, presented by Miss L. Cox ; a Greek Tor- 

 toise ( Tcstudo ^raeca) from South Europe, presented by Mr. 

 Balfour Read ; a Neumann's Baboon [Cynocephalus nettmaniii) 

 from Central Africa, a Nisnas Monkey (Cercopithecus pyrrho- 

 iiotiis) from East Africa, a Striped Hyjena {Hyaena striata, 

 var. ) from North Africa, three Pale Fennec Foxes {Cams pal- 

 lidits) from the Soudan ; a Brazilian Caracara {Polyboriis bra- 

 siliensis) from South America, a Black-headed Conure {C(7//M;'i(.r 

 nanday) from Paraguay, an Egyptian Monitor ( Varianus 

 «//(j/2Vhj) from North Africa, two Brazilian Tortoises (T^x^^rfo 

 tabulata) from South America, two Sculptured Terrapins 

 (Clemmys inscnlpta) Uom'NQt^M America, three Muhlenberg's 

 Terrapins {Clemmys muhlenbergi) from North America, a 

 Pennsylvania Mud Terrapin (Cinosterniiin pennsylvanic ttm) 

 from North America, three Laughing Kingfishers {Dacelo 

 gigantea) from Australia, two White-capped Tanagers {Stepha- 

 rophorus leticocephalus) from Argentina, three Striated Tanagers 

 Tanagra striata) from Buenos Ayres, four Palm Tanagers 

 {Tanagra palmarium) from South America, a King Snake 

 {Coronella geliila) from North America, two Ocellated Sand 

 Skinks ( Chalcides occllatits) from North Africa, deposited ; four 

 Lesser Snow Geese {Chen nivalis) from North America, two 

 Mute Swans (Cygnus olor), European, purchased ; a Thar 

 (Hemitragus jemlaicus), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Spectrum of Nova Peusei. — A communication from 

 Prof. Pickering to the Astronomische Nachrichten (Bd. 156, 

 No. 3735) gives particulars of the examination of recent photo- 

 graphs of the spectrum of the Nova taken at the Harvard Col- 

 lege Observatory. The reductions show that, as has been the 

 case in previous Novx-, the object has been gradually changing 

 into a gaseous nebula. The resemblance to the nebula 

 N.G.C. 3918 was so close on June 20 that no marked difference 

 in the two spectra was noticeable. The main point of divergence 

 is in the relative intensity of the chief nebular line at A.5007, 

 which in N.G.C. 391S is about eight times as bright as H5, 

 while in the Nova these two lines are about equal in intensity. 

 The following lines are common to both bodies : — 



3869 468S 



3970, He 4862, H6 



4102, HB 4959 



434 1, H7 5007 



and with the above-mentioned exception of A5007 are of similar 

 intensity. Four bright lines between H7 and H;3 appear faintly 



NO. 1662, VOL. 64] 



in the Nova, and are not present in the nebula, while one, at 

 A4364, is seen in the nebula, but not in the Nova, perhaps 

 owing to the proximity of H7. 



New Double Stars. — Bulletin No. 3, from the Lick 

 Observatory, contains a list of 94 new double stars discovered 

 by Mr. R. G. Aitken, with the 12-inch and 35-inch telescopes, 

 the majority of the measures being obtained with the larger 

 instrument. The series has been compared with Prof. Burn- 

 ham's Catalogue to ensure the absence of duplicate records of 

 previous discoveries. Classified according to distance of their 

 components the 94 pairs show the following grouping : — 



Under o'25 .. 3 



0-50 23 



I'oo 47 



200 73 



Over 5-00 I 



Six Stars with Variable Radial Velocity. — Prof. 

 W. W. Campbell gives particulars in Bulletin No. 4 of the 

 Lick Observatory of six additional spectroscopic binaries, of which 

 variable velocity in the line of sight has been determined from 

 spectra obtained with the Mills spectrograph of the Lick 

 Observatory. The details of the measures are given below : — 



Star. Extreme velocities 



(kilometres). 



I Cephei ... -37 ... -5 



Oi3i Cygni ... -12 ... +3 



5 Piscium ... -f25 ... -t-35 



T Persei ... -h 10 ... -4 



I, Ceti ... -9 ... +4 



t Hydrse ... -f43 ... -f 32 



Causes of the Variability of Earthshine. — In the 



May number of the U.S. Monthly Weather Review, Mr. 



H. H. Kimball gives an interesting discussion of the probable 



causes of the earthshine observed on the moon's shadow side 



some few days previous to, and following new moon. With the 



idea that the amount of light reflected from the earth to the 



moon will vary considerably according to the condition of the 



earth's surface and atmosphere, a special projection chart of 



the earth has been prepared, showing the configuration of the 



continents, oceans, &c. , and general atmospheric conditions 



(clouds, &c. ), on a certain evening when the earthshine was 



specially prominent. If the bright portion is snow-covered, it 



will reflect more th.in a continent of forest and vegetation, and 



much more than a large extent of water. 



A factor of considerable importance is the varying distance 

 of the moon, and it is stated that 52 per cent, of the change 

 in intensity of the earthshine is due to the eccentricity of the 

 moon's orbit, and this is probably much greater than could 

 be expected from any increase or diminution in the average 

 cloudiness over the hemisphere of the earth reflecting light to the 



SOLAR RADIATION. 

 COLAR radiation is a subject which has more than scientific 

 ^ interest. It is the source of all the energy which maintains 

 the economy of our globe. It lights and heats the other members 

 of the planetary system. But, after accomplishing this, only an 

 infinitesimal proportion of the total radiation has been used. 

 The remainder, in so far as we know, is wasted by uninterrupted 

 dissipation into space. 



The subject can be regarded and studied from either the solar 

 or the terrestrial point of view. In terrestrial physics every- 

 thing may be said to depend on the energy which, in one form 

 or another, is supplied by the sun's rays. It is the revenue of 

 the world, and it is of fundamental importance for us to know 

 at what rate it falls to be received. 



Roughly speaking, the surface of the earth is occupied to the 

 extent of one-fourth by land and three-fourths by sea. There- 

 fore at least three-fourths of the surface which the earth presents 

 to the sun is at the sea-level. Consequently the rate at which 

 the sun's radiant heat arrives at the sea-level is the fact which it 

 is of the greatest economical importance to ascertain. 



In considering this problem we have to answer two questions : 

 What is the best experimental method of determining the 

 heating power of the sun's rays at any place ? and What is the 

 best locality for making the experiment ? Let us take the last 

 first. The energy which a radiation communicates to a surface 



