380 
version temperature for air, however, calculated by 
Witkowski from the empirical formula of Rose-Innes, was 
+360°, whilst the van der Waals formula was found to 
require an inversion temperature of + 500°; in the latter 
case, however, the calculation is based on the assumption 
of a small difference of pressure (1 atmosphere) accom- 
panying the expansion, whilst the experimental values refer 
to expansion over a wide range of pressure. The shape 
of the curve for air connecting the inversion temperature 
with the initial pressure at which expansion occurs shows 
that below So atmospheres a rapid fall of the inversion 
temperature occurs as the pressure is diminished. Very 
little cooling effect is therefore to be anticipated with air 
allowed to expand from pressures below 80 atmospheres ; 
such, indeed, is actually observed to be the case, liquefac- 
tion only taking place readily in the apparatus described 
by Prof. Olszewski in 1902, so long as the initial pressure 
does not fall below this limit. 
STUDENTS IN GERMAN UNIVERSITIES. 
CCORDING to the Chemiker Zeitung, the total number 
of matriculated students in attendance at the German 
universities during the present winter semester is 45,136, as 
against 44,942 last summer, and 42,390 in the preceding 
winter; five years ago the attendance was 35,518, ten 
years ago 30,043, ‘twenty years ago 27,080, and thirty 
years ago, that is, in the winter 1876-7, it was only 
17,457, upon which total the present number shows an 
increase of 27,679, or 159 per cent. It is of more than 
passing interest to compare the number of students at the 
+ 
different universities to-day with those of thirty years 
ago :— 
1906- 1876- 1906- 1876- 
. 1907 1877 | ee 1907 1877 
Berlin... ... 8188 ... 2490 | Tiibingen 1522.0) 1908 
Munich... ... 5567 .. 1280 | Marburg Th OS tees oe 
. Leipzig ... . 4406 ... 3026 | Wiirzburg 1407 ... 1028 
Bonn 520028008703, ena 24 aa 2715) meARO 
Halle 2250... 854 | Konigsburg ... 1140 ... 621 
Breslau ... 1961 ... 1219 | Giessen ... TOO7,... 318 
Gottingen 1831 ... 991 | Erlangen 1056... 474 
Freiburg 1744 ... 293 | Kiel ne SIT gree Pil) 
Strassburg 1652 ... 707 | Greifswald 827 ... 468 
Heidelberg 1603 ... 473 | Rostock... 645 ... 156 
Miinster... YOR eos LS 
The distribution of these students in the various branches 
of academic study is as follows :— 
1906-1907 1876-1877 
Law students 12215 4835 
Art students 10873 3874 
Medical students .. 7035 3374 
Mathematical and science students 6116 2009 
Evangelical theology... a son 2208 1518 
Pharmaceutical students Bae aes LOGS 680 
Catholic theology : oS eo ZOS 1164 
Students of economic sciences and 
forestry 1235 155 
Agricultural science 985) ns 369 
Dentistry . x 870) oa. 8 
Veterinary Science (only matriculated at 
Giessen) LEO a: fo) 
Against these numbers it is to be remarked that the large 
number of applied and pure science students attending the 
Technische Hochschulen is not included here, while the 
number of arts students is too high by nearly 1000, owing 
to the modern custom in the Prussian universities’ returns 
of including among such students those whom they place 
under the tabulation heading ‘‘ Sonstige Studienfacher der 
philosophischen Facultat.’’ 
Out of a total number of 45,136 students in attend- 
ance at German universities during the present winter half- 
year, 4151, or 9-2 per cent., are described as foreigners, 
against 8-6, 8-4, and 7-5 per cent. in the preceding half- 
years. The absolute increase of 596 on the number for 
the corresponding semester of last year (namely, 3555) 
is almost exclusively due to an increase in the num- 
ber of Russian students, who have increased from 
1326 to 1890 in one year. Of the 3717 students belonging 
NO. 1946, VOL. 75 
NEAT 
[ FEBRUARY 14, 1907 
to European countries, 681 are from Austria, 341 from 
Switzerland, 144 from England, 139 from Bulgaria, 83 froma 
Roumania, 6: from Servia, 58 from France, 57 from 
Holland, 53 from Luxemburg, 47 from Greece, 40 from 
| Turkey, 33 from Italy, 32 from Scandinavia, 23 from 
Spain, 19 from Belgium, 9 from Portugal, and 5 from 
Denmark. From America, mainly from the United States, 
are 302; from Asia, chiefly Japanese, 113; from Africa, 
13; and from Australia 6. The distribution of this foreign 
element at the universities is as follows :— 
Foreign students Foreign students 
-- ee oe 
University Number Per cent. University Number Per cent. 
Berlin 1189 14°5 Giessen... 84 76 
Leipzig ... 062 14°8 Breslau. 77 3°9 
Miinich ... 496 8S Wiirzburg 67 4°7 
Heidelberg 259 16°1 Marburg 60 4°9 
Halle 254 ines} Tiibingen 59 3°9 
| Jena NES) soog MLYALS) Greifswald 43 5°2 
Gottingen 169 ... 9'2 Erlangen 28 26 
Freiburg TORN. | OR Rostock 13 2°0 
Konigsberg 134 ... 117 Kerelinee PSS © iT 
Strassburg 96 ... 5°8 Munster TI nc. Og 
Bonn SS... 2 
These foreign students are taking as their chief studies :— 
evangelical theology, 185; Catholic theology, 34; law, 580; 
medicine, 1080; philosophy, languages, or history, 951; 
mathematics and science, 714; agricultural sciences, 
forestry, &c., 573; dentistry, 24. 
STANDARD ELECTRIC GLOW LAMPS. 
‘THE report of the Engineering Standards Committee on 
the British standard specification for carbon filament 
glow lamps, which has recently been issued, is of great 
interest, more especially as it has been published at a time 
when so many important papers and discussions on carbon 
and metallic filament lamps are occupying the attention of 
men of science and engineers. The specification gives at 
the beginning a list of standards and definitions, and goes 
on to state what the committee has decided as to the 
tests a standard lamp shall comply with. A lamp of 
12 candle-power is suggested in addition to the usual 8, 
16, 25, and 32, and this should prove a very useful size ; 
although it has already been used, it has not been kept 
as a stock lamp usually. The standard lamps are to be 
divided into two classes, having a useful life of goo and 
800 hours respectively, and all lamps purporting to be 
British standard lamps are to be marked with the trade 
mark or name of manufacturer, the standard mean hori- 
zontal candle-power, the voltage, and a reference letter in 
a circle, which is to show which class—whether 400 or 
Soo hours—the lamp is intended for. This reference letter 
is, we think, a mistake, as the ordinary consumer will not 
know to what it refers, and we do not see the objection 
to marking plainly on the lamp the useful life hours. The 
insulation resistance between cap and filament seems to 
us to be rather high (1000 megohms). The limits for 
mean horizontal candle-power and total watts, on the 
other hand, allow plenty of margin, but doubtless these 
will be reduced after the standards have come into force, 
which we understand they will do in July next. At pre- 
sent, however, we do not see that the ordinary consumer 
will benefit very greatly by the specification when it does 
come’ into force, for, as we pointed out a few months 
back, unless the borough councils or local authorities erect 
special testing laboratories where tests on lamps can be 
carried out by an expert for a very small fee, or even 
free of cost, the ordinary consumer will be in practically 
the same position as he is at present. Of course, the fact 
of his being able to ask for a standard lamp may tend to 
make the article sold him slightly better, and with truer 
candle-power and consumption figures marked on; still, we 
are afraid that, from the consumer’s point of view, until 
he can get his. lamps tested locally, not very much 
improvement will be seen. The report is, however, of 
very Sreat interest to those connected with that branch of 
the electrical profession, and is certainly a long step in 
j the right direction. 
