July 27, 1882] 



NATURE 



307 



physical properties, between isomorplious sub-lances and gases, 

 is suggested ; and a law similar to Avogadro's may be applicable, 

 viz., equal volumes of tho.-e (isomorplious) substances must con- 

 tain the sime number of molecules. In verification of this is 

 the fact shown by M. Spring, that the quot ents i f the specific 

 weights of the alums by the respeclive molecular weights are 

 equal. Thus the law of Avogadro, verified hitherto in its con- 

 sequences only for gases, may be found to strike itsioots even into 

 solid bodies, and the problem of determining the molecular mag- 

 nitudes of the latter may one day receive a solution conforn ably 

 to modern theories of chemistry. M. Spring is extending 

 his examination to other isomorphous substances, and will also 

 study the ratio of expansion and contraction in heteiomorphous 

 bodies. 



The third instalment of Dr. Hermann Midler's "Further 

 Observations on the P'ertilisation of Flowers by Insects" is 

 occupied by observations, supplementary to those recorded in 

 his " Befruchlung der Blumen durch Insekten," on the insects 

 which visit particular species and assist in their pollination, with 

 some notes on corresponding peculiarities of sructure in the 

 Bowers themselves. It is illustrated by a very beautifully 

 executed plate. 



The additions to the Zoolog'cal Society's Gardens during the 

 past week include a Macaque Monkey (Macaais cytiomolgus) 

 from India, presented by Lady Parkyns ; an Egyptian Fox 

 (Cants nihticus) from Egypt, presented by Mr. Horace Kemp ; 

 two Coypu Rats (Myopotamns coypus) from South America, two 

 Common Night Herons (Nycticorax griscus), European, pre- 

 sented by Mr. A. A. van Bemmelen ; two California!] Quails 

 (Callipipla California*) from California, presented by Mr. J. 

 Biehl ; a Crocodile (Crocodilus, sp. inc.) from Black River, pre- 

 sented by Mrs. A. II. Jamrach ; an .^sculapian Snake (Coluber 

 asculapii) from Central Europe, presented by Lord Arthur 

 Russell, M.P. ; two Australian Fruit Bats (Ptcropus polioce- 

 phalus), a Black-breasted Peewit (Sarciopliorus pectoralis), an 

 Australian Monitor (Monitor gotildi) from Australia, two Porto 

 Rico Pigeons (Columba corensis) from the West Indies, a South 

 American Jabiru (Afyetiria americana), two Brown Thrushes 

 ( Turdus Seucomelas) from South America, two Demoiselle 

 Cranes (A nt/iropoides virgo) from North Africa, three Blue- 

 shouldend Tanagers (Tana^ra cyanoplera), a Striated Tan- 

 ager (Tanagra striata), a Tanager (Saltator, sp. inc.) from 

 Brazil, two Scops Owls (Scops asio) from North America, 

 two Yellow Sparrows (Passer luteus) from East Africa, two 

 Beautiful Waxbills (Estrelda formoia) from India, pur- 

 chased ; a Two-spotted Paradoxure (Nandinia biiwtala), a 

 Hybrid Sclater's Muntjac (between Cervulus muntjac 9 and 

 Cerz'iiius lacrymans & ), born in the Gardens. The following 

 insects have emerged in the Insect House during the past two 

 weeks : — Silk Moths : Actios selene, Telea polyphemus, Telea 

 promethea ; Moths : Ccratocampa imperialis, Bombyx castrensis, 

 Zygana filipendulce, Liparis monacha, Dcilephila vespcrtilio, 

 Deilephila euphorbia, Bcmbccia hylwi/onnis, Plusia concha; 

 Butterflies : Parnassius apol/o, Mclanagria galaihea, Goneopteryx 

 rhamni, Vanessa io, Vanessa polychlorus, Araschnia levana var. 

 prorsa, Theela betuLc, Theela spina, Epinephde janira, Enbia 

 b.'andina. 



OUR ASTRONOMICAL COLUMN 



The Wedge Photometer. — In a communication to the 

 American Academy of Arts and Sciences in May last (Nature, 

 vol. xxvi. p. 259), Prof. Pickering has some remarks upon the 

 use of a wedge of shaded glass as a means of measuring the light 

 of the stars. Pie considers that, while it has been maintained by 

 some writers that it is not a new device, " the credit for its intro- 

 duction as a practical method of stellar photometry seems clearly 



to belong to Prof. Pritchard, director of the University Observa- 

 tory, Oxford." Various theoretical objections to this photo- 

 meter have been advanced, and many sources of error suggested, 

 but Piof. Pritchard has made the best possible reply to them by 

 measuring a number of stars, and showing that his results are in 

 very close agreement with others obtained elsewhere by wholly 

 different methods. His photometer "consists of a wedge of 

 shade glass of a neutral tint inserted in the field of the telescope, 

 and movable, so that a star may be viewed through the thicker 

 or thinner portions at will. The exact position is indicated by 

 means of scale." The measure of the brightness of the star is 

 made by bringing it to the centre of the field and moving the 

 wedge from the thin towards the thick end until the star disap- 

 pears. Stars mu-t always be kept in the centre of field to insure 

 the readings being comparable. But Prof. Pickering makes the 

 ingenious suggestion that this photometer may be further simpli- 

 fied by su sir uting the earth's diurnal notion as a measure of 

 the position of ihe star in the wedge at disappearance. " .t is 

 only necessary to insert in the field a bar parallel to the edge of 

 the wedge, and place it at ri^ht angles to the diurnal motion, so 

 that a star in its transit across the fiebl will [ass behind the bar 

 and undergo a continually increasing absorption as it passes 

 towards the thicker portion of the wedge. It will thus grow 

 fainter and fainter, until it finally disappears." Then the 

 interval of time from the passage behind the bar until the star 

 ceases to be visible becomes a measure of its light, and the time 

 will vary with the magnitude. As in Prof . Pritchard's form of 

 the instrument, it is only necessary to determine the value of a 

 single constant. Prof. Pickering adds some suggestions with 

 regard to observations with this photometer, and recommends 

 them to the attention of amateurs. 



j The Observatory in Vale College, U.S. — Prof. H. A. 



i Newton, who wa- appointed Director of the Winchester Obser- 

 vatory in Vale College, New Haven, U.S., in May last, has 

 drawn up a report on the present state of ihis establishment, and 

 of the preparations in progress for placing the instruments in 

 new buildings specially erected to receive them. The heliometer 

 ordered from Repsold, of Hamburg, two years since, was re- 

 ceived last spring ; the cost, including freight, and other expenses 

 to New Haven, being close upon 7460 dollars. To supplement 

 the heliometer, and also for independent work, an equatorial 

 telescope of 8 inches diameter was ordered from Mr. Howard 

 Grubb of Dublin, and is expected in August. (No mention is 

 made by Prof. Newton of the 9- inch Alvan Clark refractor, 

 which Yale College was stated to possess in the Smithsonian 

 report on astronomical observations in 1880). About nine acres 

 from the southern extremity of the observatory lands have been 

 set apart as a site for the observatory, and the erection of two 

 towers for the heliometer and equatorial respectively, has been 

 commenced. The heliometer tower was expected to be ready 

 for the instrument early in July, the dome constructed by Mr. 

 Grubb having been already put in place. It is intended by 

 Prof. Newton to undertake such work with it, immediately it is 

 available, as shall prepare for the most advantageous use of the 

 instrument during the approaching transit of Venus. In the 

 Smithsonian report referred to, the diameter of the object glass 

 is staled to be 6 inches. 



The income derived from the fund set apart by the late Hon. 

 O. F. Winchester, is to be applied for the maintenance of the 

 observatory. The 8-inch equatorial has been purchased from 

 funds generou-ly provided by a private individual, who for the 

 present does not desire his name to be mentioned. Under the 

 direction of Prof. H. A Newton, supported by such liberaliiy, 

 astronomers will look forwaid to a bright future for the "Ob- 

 servatory in Yale College" — as, v.ith the assent of Mr. Win- 

 chester's family, the institution is to be called. 



The Transit of Venus. — In consequence of the sudden 

 death of Mr. Burton, who, as we mentioned last week, had been 

 appointed observer at Aberdeen Road, Cape Colony, we under- 

 stand Mr.A. Marth will have charge of that station. 



It is not improbable that some readers may contemplate pro- 

 ceeding for the purpose of observing this phenomenon (which 

 will not recur fill the year 2004), where it is visible from ingress 

 to egress, and perhaps with a view at the same time of escaping 

 a w inter in this climate. !f such there be, they might not readily 

 fix upon a more advantageous station than the Blue Mountain 

 ran»e in the island of Jamaica or its vicinity. Calculating for a 

 point in longitude 77° 30' W., latitude 1S 5' N., the times of 

 contacts and sun's altitudes ere as follows : — 



