312 
sides, the solar dials could be used to obtain the 
hour during the night by the shadow of the moon; 
and indeed the time at night could be obtained by 
observation of the fixed stars. The same table con- 
tains the value of the equation of clocks and pen- 
dulums, what we now call the “ equation of time.” 
5. A summary of the movements of all the planets for the 
year, containing little but an indication of the epochs 
when they were visible and of the constellations through 
which they passed. 6. A plate in which the preceding 
data were graphically traced. 7. A tabie of the latitudes 
and longitudes (adjusted to the meridian of Paris) of the 
principal cities of France. 8. An appendix, relating to 
physical questions, containing an account of the winds 
which prevailed in Paris for every day of the preceding 
year, and an exact account of barometric indications for 
the same period. 
In 1680, Picard completed his volume by the follow- 
ing additions :—A note on the inquiry into longitudes 
(recherches des longitudes) by means of clocks and pen- 
dulums ; a table of lengths of the pendulum corresponding 
to an increasing number of vibrations per second, and in- 
tended for the regulation of clocks ; a table of declinations 
of the sun for each day (by degrees and minutes) ; and 
lastly, a table indicating the weights of the unit of volume 
(a cubic foot) of different substances. 
These Ephemerides, although less complete, so far as 
pure astronomy is concerned, than those of Hecker, were, 
however, superior to them from a practical point of view, 
by the-substitution of the right ascension of the sun and 
moon for the longitude and latitude of these bodies ; it is, 
in fact, the right ascension and declination which are 
directly useful to astronomers. 
Picard, who published the “ Connaissance des Temps ” 
at his own expense and his own risk, was naturally inte- 
rested in the success of his work. Thus, after having 
sought to satisfy the wants of astronomers and mariners, 
he added to this publication a list of the days on which the 
posts to the various towns of France set out from Paris. 
The custom of adding to the astronomical tables physical 
or statistical data altogether foreign to astronomy, has 
been continued to the present time in the “ Annuaire du 
Bureau des Longitudes.” 
Still the great labour required in editing these Epheme- 
rides soon tired the Abbé Picard, who tried to find a 
successor. There was then at the college of Lisieux, at 
Paris, a professor of rhetoric named Pierre, who was a 
good astronomer, and on that account was intimate with 
all the astronomers of his time. Thelearned Abbé asked 
him one day if he knew any one capable of assisting him, 
and afterwards of carrying on the “Connaissance des 
Temps ;” Pierre proposed Jean Lefebvre, weaver at 
Lisieux, who, in the intervals of leisure which his work 
allowed him, amused himself by reading some books on 
astronomy, and was familiar enough with that science to 
be known to Pierre, originally of the same town : he had 
sent the latter, among other things, calculations of eclipses 
which quite agreed with observation. Pierre and Picard 
then asked Lefebvre to calculate a table of the passage of 
the moon across the meridian, and this having been 
accurately performed, they offered him an academician’s 
annuity to come to Paris and continue the “ Connais- 
sance des Temps.” We owe to his calculations the 
volumes from 1684 to 1702. Profiting by the new tables 
of the equation of the sun of Picard and Cassini, he was 
able to calculate the ‘ Connaissance des Temps” with 
more accuracy than had ever been done before. 
To Lefebvre also are due several additions and modifi- 
cations. Thus in 1686 he added a table of the exact posi- 
tions of the planets, the sun, and the moon for every ten 
days ; in 1690 he gave the immersions and emergences of 
the first satellite of Jupiter ; im 1691 maxims in reference 
to the movement of a ship, a list of ports and coasts, &c. 
In 1692 he added a table of refractions from 0° to 90° of 
NATURE 
[Aug. 14, 1873 
apparent height, calculated to a minute up to 48° and to 
a second from 48° to 90°, as well as a value of the declina- 
tion of the needle according to the observation of La 
Hire. 
In 1693 Lefebvre, having left Paris to take part in the 
geodetic operations of Picard, one of his colleagues of the 
Academy, Lieutaud, edited the Comnatssance des Temps 
in 1693 and 1694; but on his return he resumed the edi- 
torship, and continued it without interruption till 1702. 
At that time, in consequence of an incident curious 
enough to bear relation, the publication of the Connazs- 
sance aes Temps was taken up by the Academy of 
Sciences. 
The son of De Ja Hire, a very popular academician, 
who had considerable influence among his colleagues, 
published, for 1701, a collection of Ephemerides intended 
to rival those of Lefebvre, in which he said, “I hope, at 
least, that there will not be found here errors (é/o¢gnements) 
of calculation so great as are seen in certain popular and 
much praised Ephemerides,” &c. Wounded to the quick 
by such a reproach, altogether untrue, Lefebvre wrote in 
the preface of the Conmatssance, for 17c1, “I cannot 
avoid replying to the invectives of a certain small novice 
[De la Hire //s], supposed author of an annual Epheme- 
rides published a short time ago. This new author, filled 
with a spirit of vanity, presumption, and falsehood. . . 
We reply to this youthful novice . . .” 
De la Hire, himself, was not spared. At this uncouth 
reply the enemy’s camp winced, and resolved on re- 
venge ; success was easy, for Lefebvre was by no means 
a general favourite. Little by little the meetings of the 
Academy were rendered insupportable to him, and when 
he had absented himself for a certain number of meetings, 
his name was struck out of the lists of that body. De- 
prived of his Academician’s pension, Lefebvre could no 
longer continue the Connatssance des Temps. The 
Academy then took possession of the publication, which 
became a public undertaking; so that the volume of 
1702, instead of being, like the previous ones, dedicated 
to the king, is published “by order of the Academy of 
Sciences.” The old title is changed, and it is simply 
called “ Connaissance des Temps, pour le Méridien de 
: Paris,” 
(To be continued.) 
NOTES 
In reference to the meeting of the British Association at 
Bradford, the Reception Room will be opened on Monday, 
September 15, at 1 P.M., and on the following days at 8 A.M., 
for the issue of tickets to members, associates, and ladies, and 
for supplying lists and prices of lodgings, and other information, 
to strangers on their arrival. No tickets will be issued after 
6 p.M. On and after Monday, September 15, members, and 
persons desirous of becoming members or associates, or of ob- 
taining ladies’ tickets, are requested to make application in this 
room. In the Reception Room there will be offices for supply- 
ing information regarding the proceedings of the meeting. The 
“Journal,” containing announcements of the arrangements for 
each day, will be laid on the table on Wednesday, September 
17, and the following mornings, at 8 a.M., for gratuitous distri- _ 
bution, Lists of members present will be issued as soon as 
possible after the meeting, and will be placed in the same room 
for distribution. The first general meeting will be held on 
Wednesday, September 17, at 8 P.M. precisely, when Dr, Car- 
penter, LL.D, F.R.S., &c., will resign the chair, and the 
President Elect will assume the presidency, and deliver an ad- 
dress. On Thursday evening, September 18, at 8 P.M., a 
Soirée ; on Friday evening, September 19, at 8.30 P.M., a Dis- 
course ; on Monday evening, September 22, at 8.30 P.M., a Dis- 
course ; on Tuesday eyening, September 23, at 8 P,M., a Soirée; 
