120 
NATURE 
[Fune 15, 1871 

or blended with each other by insensible gradations, are 
primé facie entitled to the rank of species.” (British 
Conchology, vol. i., Introduction, p. xix). Now we may 
see several species of Azssoa living under the same stone 
between tide-marks, several species of Zzz7@a in the same 
stream or ditch, and more than one species of He/ix feeding 
together on the same leaf. In such cases there is no 
fusion or confusion of species ; each has its own definite 
limits, and retains its own peculiar characters. I say 
nothing of genera and more comprehensive groups which 
form communities in a still more diversified fashion, but 
are equally free from intermixture. 
J. GWYN JEFFREYS 


OUR BOOK SHELF 
Echinidesdu Département de la Sarthe, considérés au point 
de vue zoologigue et stratigraphique. Par Cotteau et 
Triger. (Paris: Bailliére, 1855-1869. London: Wil- 
liams and Norgate.) 
WE fear that some time must elapse before science will 
resume its place in unhappy France; but in the mean- 
time its professors, who are innocent of the mischievous 
and insane acts which have caused so much ruin, demand 
our heartfelt sympathy. M. Cotteau, of Auxerre, whose 
work we are about to notice, is well known to English 
geologists, and is highly esteemed by them for his long 
and conscientious labours in the field of Mesozoic 
echinology. His coadjutor, M. Triger, died during the 
progress of the work. It consists of two royal octavo 
volumes, one containing an account of Echinoderms found 
in the Jurassic and Cretaceous formations in the Depart- 
ment of the Sarthe, the other having sixty-five well- 
executed plates of species, besides several charts to show 
their geological and stratigraphical, distribution. It 
appears from the preface that this most creditable pro- 
duction of French palzontology was commenced in 1857, 
and finished in 1869. We therefore regret to observe 
that M. Cotteau was notaware of Dr. Wright’s admirable 
monograph on British fossil Echinodermata, which was 
published by our Palzontographical Society in 1856, and 
which goes over a great deal of the same ground as M. 
Cotteau. Had the latter author consulted it, he would 
probably have avoided some mistakes, e.g. in attributing 
the specific name of Pseuvdodiadema hemisphericum to 
Desor instead of to Agassiz. A comparison of the figures 
of this and other species given in both works is decidedly 
favourable to the British artist (Mr. Bone) as regards 
accuracy and completeness, although MM. Levasseur and 
Humbert are deservedly eminent in their style of litho- 
graphy. 
The Echinoderms found in the Jurassic and Cretaceous 
formations must have inhabited a soft bottom in seas of 
considerable depth, judging from the present habits of 
allied species ; and their variability was not less in those 
remote periods of the world’s history than it was in the 
epochs which preceded and followed. Ley 


LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his Correspondents. No notice is taken of anonymous 
communications. | 
The Paris Observatory 
HAVING read only yesterday the agonising account written by 
M. Marie-Davy and countersigned by M. Delaunay, descriptive 
of the Communists having made the Paris Observatory one of | 
their chief strategical points, of the domes of the observatory 
having five hundred bullet-holes through them, and of the rabid 
attempts made by the citizens in arms, before retiring on the ap- 



proach of the Versaillists, to burn or blow up the whole building, 
I am not a little surprised to find in NATURE of June 8, received 
here this morning, a statement to the effect ‘‘that the Paris Ob- 
servatory had suffered scarcely any injury up to the end of the 
second siege. No delegate of the Commune had presented him- 
self either to take possession of it or to blow it up.” 
I presume that you wrote in ignorance of the real facts, and 
perhaps not without some intention of whitewashing the poor 
Communists from the exaggerated denunciations which have been 
poured on them since their fall ; yet neither they nor you should 
object to true accounts of what they actually did while in power 
appearing before the world without menace and without favour, 
The mere showing of the Commune during this second siege, 
and still more its international organisation, seems to have sur- 
prised most persons; yet the character of the association, and 
its imminence under the feet of all the Governments of Europe, 
was duly noted in the section on Metrological Legislation of 
my report presented to the Board of Visitors of the Royal Ob- 
servatory, Edinburgh, in June 1870; the association, though 
political, having obtained mention there on account of its having 
adopted the scientific metrical system of weights and measures, 
and professing to find it a most efficient agent for assisting in 
breaking down the barriers between nations, and rooting up 
traditional customs and beliefs. I must confess, however, that 
I was not prepared for these revolutionaries taking up so very 
early in their outward career, as this their first and just-concluded 
essay in Paris, the chronological department of the metrical 
system, thereby repudiating, as the order found on General 
Delescluze indubitably shows, both the Christian Era and the 
accustomed months, for decimal periods of days and the era of 
the first French Revolution. In my book, ‘‘ Our Inheritance in 
the Great Pyramid,” published in 1864, I did indeed remind 
that that most revolutionary method in chronology was originally 
a part of the metrical system, and though deposed under Napoleon 
Bonaparte, might be expected to reappear when the present pro- 
moters of French metrology in this country had acquired more 
boldness; but here is the accomplished fact upon us at this very 
moment, and it would be well for all those metrical agitators 
who were so loud at the British Association last summer in 
Liverpool in their outcries to Government to make the metrical 
system compulsory throughout this country, now to declare 
honestly whether they are inwardly with the Communists in de- 
siring ultimately the abolition of the Christian era and the de- 
struction of the week of seven days. C, Prazzi SMYTH 
15, Royal Terrace, Edinburgh, June 9 
Science Lectures for the People 
Ir is all very well to say, Let our children be taught science 
in the schools; but that does not meet the need of a large 
section of the nation, the product of the schools of a former 
generation. | Many hard-worked men who had no scientific 
teaching whilst at school, have now acquired the wish to know 
more of nature’s mysteries, but know not whither to turn for aid. 
Books are plentiful, but it is very tiresome to wade through dry 
pages, scientifically dried of their sap by the use of terms which 
are not commonly understood—especially after the wearying 
labours of the day. Experimental lectures, like those at the 
Royal Institution, but a little more specialised, are wanted for 
popular use ; the question is, How are we to get them? Are 
we to go to Government for aid, or shall we bestir ourselves and 
voluntarily endow these lectures ? 
Surely Huxley or Tyndall would be quite as much sought after 
as Spurgeon if they came forward and announced a series of 
lectures ; St. James’s Hall would be as crowded as the Tabernacle 
if they held a weekly lecture ; pew-rents would be as certain of 
collection from scientific as from religious devotees. Those 
busily engaged professors can indeed hardly be asked to under- 
take such a task as this ; but any competent man of science, able 
to explain the facts of science in popular language, might reckon 
on public support if he made such a venture as this. Let him, 
for example, give a series of twelye lectures on Biology, as it 
affects our daily existence; not wandering into the remote 
regions of extraordinary phenomena, but simply expounding 
ordinary life laws. Here would be a subject refreshingly new 
and interesting to thousands of City-born and bred toilers. 
The lectures, if on week days, must be after office hours— 
from nine o’clock to ten, say ; and in some hall easily accessible, 
as St. James’s. GEORGE FRASER 
169, Camden Road, N. W. 

