May 16, 1884.] 
was given to barometric and thermometric condi- 
tions. <A fifth chart gives the average direction of 
the currents for the year. — 
Four years later (1872), these were given more ex- 
tended form in the ‘ Wind and current charts for the 
Pacific, Atlantic, and Indian Oceans,’ about on the 
same plan as before, but with the addition of iso- 
thermal and isobaric lines in small side charts, after 
the pattern of those prepared by Dove and Buchan. 
Part of the information in these charts was super- 
seded, in 1872, by a volume giving monthly maps 
of ‘Currents and surface-temperatures of the North 
Atlantic Ocean, from the equator to latitude 40° 
north,’ prepared by R. Strachan, under the direction 
of R. H. Scott of the meteorological office. This is 
still the best work on North Atlantic currents 
and temperatures. The averages are here given 
for two-and-a-half-degree squares, from Maury’s 
charts, Dutch observations, and some other 
sources, with the number of observations on 
which they are based. It is very evident from 
this, that the currents, especially, need a much 
more extended examination than they have yet 
received, especially when one recalls the irregu- 
lar variations lately determined by Commander 
Bartlett in so marked a current as the Gulf 
Stream. If the currents have regularly periodic 
changes, as seems probable at certain places, the 
precise determination of their form will require 
a sifting of observations down even into one- 
degree squares. 
The publications of the Dutch meteorological 
institute at Utrecht have long beenfamous. In 
addition to their extensions of part of Maury’s 
charts in 1856,1 a more independent set of 
monthly charts for the several oceans was is- 
sued a little later, on which a simple graphic 
method of showing direction and frequency of 
winds was adopted.? 
Until recent years, comparatively little origi- 
nal work on the North Atlantic was done in 
France. The British pilot charts of 1868 were 
republished, changed only by translation of the 
names and explanations from English into French. 
In 1863, Ch. Ploix published his ‘ Vents et courants, 
routes générales,’ compiled from Maury’s and other 
works. A revised edition of this was issued in 1874. 
Since then, Lieut. L. Brault, in charge of the meteoro- 
logical service of the dépét of charts and maps of the 
French marine, has undertaken extended studies of 
meteorology of the several oceans, based on twenty 
thousand selected logs (‘toute une montagne de pa- 
pier’) of French vessels, dated between 1800 and 1870, 
and independent of the work of other nations. He 
states that the average accuracy of record is much 
1 Maurij’s wind-kaart voor het oostelijk gedeelte van den 
Noorder Atlantischen Oceaan, vermeerderd mct hollandsche gege- 
vens. 
Maurij’s passaat-kaart van den Atlantischen Oceaan, vermeer- 
derd met hollandsche gegevens. 
2 12 Windkaartjes van den Noorder Atlantischen Oceaan, etc. 
These were published in the Uitkomsten van wetenschap en 
eroaring aangaande winden en zeestroomingen in sommige 
gedeelten van den oceaan. 
SCIENCE. 
595 
better than in the logs used by Maury.! His first series 
of charts gives the probable direction and intensity of 
the winds for every three months in the North and 
South Atlantic, Indian, and Pacific Oceans,?— sixteen 
sheets in all, In addition, a second series of monthly 
charts for the four oceans was to be prepared, showing 
winds, currents, rain, fog, cloudiness, squalls, storms, 
etc.; but these, I believe, arenot yet completed. The 
accompanying cut (fig. 3) shows the graphic method 
of illustration used by Brault. The number in the 
middle is the number of observation for the square 
concerned. ‘The radial bars show by their length 
the relative frequency of winds from the points of the 
compass to which they are directed. The different 
marking in these bars shows the relative frequency 
Hig. 3. 
of five grades of strength, from heavy wind to light 
breeze. The ratio of the;distance between the two 
concentric circles to the length of the longest arrow 
gives the percentage of calms. The detailed sub- 
division of winds according to their force is a special 
feature of this work. Brault notes that eighty ob- 
servations in a five-degree square give trustworthy 
results for direction within the area of the trades; 
but three or four hundred are needed for the wester- 
lies beyond the tropics. This statement is of value in 
enabling one to judge of the probable degree of pre- 
cision in charts where the number of observations 
used in averaging is candidly given. 
A valuable work, based_on Portuguese and Dutch 
1 Etude sur la circulation atmosphérique dans V Atlantique 
Nord pendant les saisons extremes. Paris, 1879. 
2 Cartes de la direction et de lintensité probable des vents 
dans l Atlantique Nord, pendant les mois de—; 1874. Jd. 
dans l’ Atlantique Sud; 1876. Jd. dans la Mer des Indes; 1879. 
Id. dans ? Océan Pacifique; 1880. 
