November, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



277 



Common Quail in Ireland. 



Mr. Allan Ellison gives a short account in the Zoolo'^ht for 

 October of the re-appearance in some nnmbersof the Common 

 Quail (Coturnix communis) in Enniscorthy,Co. Wexford, during 

 July last. This note is of interest, inasmuch as for the past 

 few years this bird has been rather scarce in Ireland. 



Solita.ry Snipe- 

 Mr. .\. R. Brooke writes to the Fidd, October 14, to record 

 the fact that a Solitary Snipe was shot on October 6 in Pem- 

 brokeshire, but no particulars as to sex or weight are given. 



An adult Great Snipe weighing 6 ozs. was shot at Snettisham 

 during the last week in September- The average weight for 

 this bird, we might remark, is about 75 ozs. 



We learn from the Field. September 30, that a Solitary Snipe 

 was shot " lately " in the middle of Ackergill Moor, near Wick. 

 The age. weight, and sex of this specimen are not stated. 



GreenlaLnd Falcons in Ireland. 



The Irish Saturalist for October contains a note by Mr. 

 H. J. Moran on the shooting of no less than eight examples of 

 he Greenland Falcon on the West Coast of Ireland during 

 this summer. Near BelmuUet two females and an immature 

 male were shot, while three others were seen of which one was 

 trapped but escaped. At the Great Skellig an adult male and 

 an adult and immature female were shot ; at Crossmoline, 

 Co. Mayo, another, sex not stated, was shot, while a young 

 female was killed in Co. Cork. Expressions of regret for this 

 slaughter are in vain. 



Icela.nd Fa-lcon in Co. Galwa-y. 



An immature female of this species was exhibited at the 

 Dublin Naturalists' Field Club in March last, which was shot 

 in Oughterard, Co. Galway. 



Honey Buzza.rd in Norfolk. 



The Field, October 7, records the fact that a Honey Buzzard 

 was shot at Snettisham, in Norfolk, " recently." The bird was 

 an immature specimen, and was killed in the act of rifling a 

 wasp's nest. 



Ma.nx-Shearwater. 



Mr. A. H. Patterson records in the Zooloe;ist for October 

 the finding of a Manx- Shearwater on the beach at Great Yar- 

 mouth, which appeared to have been dead some four days. 



In the same journal is a record of the Manx-Shearwater in 

 Worcestershire, one having been shot on a small piece of water 

 near Bromsgrove on September 16. 



PHYSICAL. 



By Alfred \V. Porter, B.Sc. 



R-egulat-rities in Spectra.. 



A NOTABLE advance has been made by Dr. Halm (Lecturer in 

 Astronomy in the University of Edinburgh) in connection with 

 the structure of spectra. Hitherto special formui:E have been 

 needed in special cases to represent the series of lines which 

 occur in spectra. Thus, for the lines on a " band " spectrum, 

 Deslandres has used the formula n = Uj, + am- where n,, is the 

 frequency of the first line (the head of the band) and m is any 

 integer ; while, for line spectra, Kayser uses either the formula 

 n = a + bm-'- + cm—* or similar expansions, and Rydberg 



the approximate formula n = a -I where a, b, and c 



(m + c)^ 

 are constants and m is any integer. The different type of 

 equation necessary for line or band spectra respectively 

 seemed to indicate that these kinds of spectra were funda- 

 mentally different from one another. Dr. Halm has now shown 

 that a single type of equation is sufficient for representing all 

 spectra, and that it represents them much better than those 

 previously used. This equation is 



— -i — = a (m + c)- + b 

 In — n 



where N, a, b, and c are constants and (as before) m is any 

 integer. When b is zero this equation is identical with Ryd- 

 berg's ; on the other hand when c is zero and b is very large 



compared with a, it approximates to Deslandres'. Curiously 

 enough a formula, of which this is merely a mathematical 

 modification, had already been employed by Thiele for band 

 spectra ; but he rejected it as inadequate. Halm shows that 

 this rejection was unwarrantable and resulted simply from 

 Thiele wishing the formula to do more than was necessary. 

 In Dr. Halm's paper most known series are carefully worked 

 out and adequately represented. For many cases the con- 

 stant c is zero (it is so for ig series out of 44). All the first 

 subsidiary series (except Mg, Ca, Sr) belong to this group. In 

 other cases c is usually a simple fraction, such as y-^. The 

 occurrence of these groups shows that remarkable relations 

 must exist between series of lines belonging to different 

 elements, but of the same group. For example let n^ be the 

 frequency of the xth line of a series, and n^' that of the same 

 line in any other series beloiif^ing to the same group ; then if 

 n and n' are any other corresponding lines in the same two 

 series and e is a constant 



- — i , = constant. 



nj - n n^' - n' 



Hence if nx, n^'^ and the constants be known the whole of the 

 second series can be calculated from the first. In this way 

 Dr. Halm calculates eleven lines in the third subordinate 

 series of Helium from the well-known Hydrogen series, for 

 both of which c is zero. An interesting geometrical relation 

 can also be exhibited. If we mark upon a straight line, on any 

 arbitrary scale, the lines of a given series in such a way that 

 the distances between two lines express the differences of the 

 corresponding frequencies, and if from any point outside we 

 draw straight paths through the points so selected, then the 

 lines of any other series belonging to the same c-group can be 

 represented as the points of intersection of those straight paths 

 with a certain transversal line. 



The following diagram will illustrate this theorem : — 



On the base line the dots show the relative positions of the 

 hydrogen lines corresponding to m = 3, 4, 5 . . .00. From 

 an arbitrary point O lines are drawn to these dots. The re- 

 maining lines have then been placed so that their points of 

 intersection with the radial lines give correctly, on the same 

 scale, the frequencies of the lines in one series for each of the 

 following substances : — Lithium, Helium, Thallium, Zinc, and 

 Indium. .\11 spectra of the same group thus drawn would ap- 

 pear to coalesce if viewed from the point O. 



In order to show that the formula is as valid for band as for 

 line spectra, Dr. Halm calculates the wave lengths of the 

 first triplet series in the line spectrum of Oxygen from the 

 wave lengths of lines in the Cyanogen band spectrum ! ! The 

 question of the regularities in spectra is obviously placed on a 

 fresh footing. 



Dr. Halm's paper appeared in the Roy. Soc. Edinh. Trans- 

 actions, July, 1905. 



[Since writing the above abstract I have discovered that this 

 formula has previously been discussed by Professor Fowler, of the 

 Royal CoUegeof Science, in T/(C/!sfi-o/'/y's/irii//oHC«n; for 1903. He 

 shows there that it is the most satisfactory formula for line-spectra. 

 He also applied it inThe A5troph}iskaljonriial{or ]anuary, iga^, to 

 the new triplets in the arc-spectrum of strontium which were 

 discovered by him. He therefore has the credit of having antici- 

 pated Dr. Halm so far as line-spectra are concerned. He does 

 not appear, however, to have applied it to band-spectra.] 



