Central Experimental Farm, 
Ottawa, December 18. 





















Tus reference is of great interest. As I have 
_ shown in the Introduction to my recent book upon 
“Age and Area,’”’ both Lyell and Hooker had con- 
ceived the ideas which I have elaborated. The 
incoming of the Darwinian theory of evolution, 
however, with its novel conception of universal 
_ gradual change, diverted effort from the lines that it 
__was beginning to follow, and to which it shows signs 
of returning, with the increasing recognition of the 
fact that gradual change is not possible in the case 
_ of most characters. Joun C. WILLIs. 
_ Zoological Nomenclature : Musca and Calliphora. 
In accordance with the rules of the International 
_ Zoological Congress, the attention of the zoological 
profession is invited to the fact that Dr. L. O. Howard, 
_ W. Dwight Pierce, and twenty-one other professional 
_zoologists have requested the International Com- 
mission on Zoological Nomenclature to exercise its 
; ox power in the case of the Linnean genus 
usca, 1758, and, under suspension of the rules, to 
declare M. domestica as type of this genus ; also, under 
_ suspension of the rules, to validate Calliphora, Des- 
voidy, 1830, with C. vomitoria as type. 
The request is based on the grounds of practical 
_ utility, and an almost unbroken history of consistent 
% since 1758 in the case of Musca, and since 1830 
_ in the case of Calliphora. It is claimed that a strict 
Bee ecetion of the rules will produce greater confusion 
‘ uniformity. 
According to the premises at present before the 
Commission, if the rules are strictly applied, the 
aie name of Musca would take either M. cesar or 
. vomitoria as type, and the species M. domestica 
would be cited either in Conostoma, 1801 [?] (type 
Ascaris conostoma=larva of M. domestica), or in 
z ma, 1802 (type Ascaris conosoma = a of 
_ M. domestica), or in Promusca, 1915 ( M.domestica), 
_ thus resulting in a very regrettable change in the 
_ homenclature of the species in question as almost 
‘universally used in entomological, zoological, medical, 
_ epidemiological, and veterinary literature. 
___ The secretary of the Commission invites any person 
_ interested in these cases of nomenclature to com- 
_ municate his opinion on the subject as soon as possible. 
_ On account of delay caused by the war, the final vote 
_ of the Commission will not be taken until about 
~ January 1, 1924. C. W. STILES 
(Secretary to Commission). 
25th and E Streets, N.W. 
Washington, D.C. 

Tesla Spectra and the Fraunhofer Effect in 
Complex Compounds. 
__. IN conjunction with Mr. W. H. McVicker, we have 
begun an investigation of the spectra emitted by the 
_ vapours of compounds when subjected to waves 
_ from a Tesla transformer passing between two glass- 
_ coated electrodes. For the sake of clarity, these 
a may be termed electro-luminescence spectra. 
___. Among the substances examined by us was benzene. 
At ordinary pressure and at the boiling-point, the 
mer of benzene emits only a fragmentary spectrum 
which seems to be built up from portions of the 
NO. 2778, VOL. 111] 
NATURE 
115 
carbon spectrum, only the strongest bands making 
their appearance. On reducing the pressure of the 
vapour, an extremely regular spectrum is emitted 
by benzene; a very regular set of band-groups, each 
of which has the same general internal structure as 
the others. Six of these band-groups lie between 
v¥=3194 and »=3752; while traces of yet another 
band-group were observed in the region beyond 3194. 
Beyond 3765, the absorptive power of the vapour 
itself cuts off part of what is evidently another set 
of band-groups. 
Each of the band-groups has the following structure: 
four strong bands, each accompanied by a weaker 
band; then two broader and weaker bands, which 
may possibly be produced by the fusion of the strong 
and weak companions of a doublet. 
The whole spectrum shows an extraordinary regu- 
larity. There are no air-lines or spark spectra traceable 
throughout its extent ; nor are there any lines visible 
on the parts of the plate unaffected by the luminescence 
spectrum. The following figures represent the wave- 
numbers of the four strong bands in each group: 
Group A. B. Cc. D. E.° F¢, 
3752 3652 3554 3454 3357 3257 
3736 3636 §= 3537 3438) = 3339 3242 
3717 3618 = 352% = 3422 3322 0 3229 
3703 3602 3504 3405 3308 3211 
For the band-groups marked with an asterisk, the 
readings on the plate were difficult—the bands being 
diffuse—and the figures are probably not exact. 
The whole of the bands in the electro-luminescence 
spectrum appear to be directly related to each other ; 
their wave-numbers are calculable from the following 
formula : 
v= 98-7120 - gb 7i2m 
6 
where » is successively equal to 33, 34, 35 -- - and 
m is successively 0, I, 2... . 
The electro-luminescence spectrum presents especial 
interest when it is compared with the fluorescence 
and absorption spectra of benzene. Hartley (Phil. 
Trans., 1908, 208, 519) and Grebe (Zeit. wiss. Phot., 
1905, 3, 363) found that the change from benzene 
vapour to a solution of benzene in alcohol produced 
a shift of 10-20 units in the position of the absorption 
bands towards the less refrangible rays. If the same 
shift be assumed to occur in the case of fluorescence, 
then it appears that the full fluorescence spectrum 
of benzene corresponds, band for band, with a part 
of the luminescence spectrum, as the following 
figures show : f 
Electro-luminescence bands 
Fluorescence bands 
3652 
3650 
v= 3454 = 3554 3752 
v+19=3454 3556 3752 
An even more surprising result is obtained by 
comparing the electro-luminescence and absorption 
spectra of benzene vapour. Hartley (loc. cit. 484) 
divides the absorption bands into four series. When 
his least refrangible bands are compared with our 
most refrangible set, the coincidence between the 
two is most remarkable. For the sake of brevity, 
only the first strong series is given here : 
Absorption bands =3650 3683 3700 3716 3734 
Luminescence bands . =3652 3686 3703 3717 3736 3752 = 3765 
Thus, if an obvious constant difference of 2 units 
between our scale-readings and those of Hartley be 
assumed, all these bands coincide within our ex- 
perimental error. 
This appears to establish that parts at least of 
the benzene absorption spectrum are replaced by 
luminous bands in the electro-luminescence emission 
spectrum, just as the dark Fraunhofer sodium line 
in the solar spectrum corresponds to the D-line in 
the emission spectrum of sodium, In other words, 
3749-S2 3761 
