Oct., 1904.] 



KNOWLEDGE & SCIENTIEIC NEWS. 



241 



position before laying; it upon the white paper which 

 was to receive tlie invisible impression. Our ilhis- 

 trations (figs. 3-4) are of the poppy and foxglove. 

 With practice, no doubt, it would be possil)le to ob- 

 tain even better results than are here given. Still tht'v 

 very fairly represent the outcome of a pro\ ision.il trial 

 to secure the reproducticMi of living plants. 



Fig. 8. — Ifnlargement of a Rolled Flnger = print. 



Wood sections are well adapted for fac-simile. 

 Fig. 6 is from a sample kindlv lent bv Dr. Russell, 

 F.R.S. 



The final illustrations (figs. 7-8) demonstrate fingei 

 printing. 



On all grounds .Mr. Sheridan deserves to be con- 

 gratulated on what we must recognise to be an 

 exceedingly interesting development in nature-printing. 



Birkbeck College. 



The new session of Birkbeck College, which l)egins on 

 Monday, October 3rd, will be opened by an address delivered 

 by Dr. Mackenzie on " The Influence of Pure Science on 

 Progress." Among those who will deliver lectures or 

 addresses on the Wednesday evenings during the coming 

 session are the Dean of Ely, Colonel Sir 'J'honias Holdich, 

 Sir Robert Ball, and the Kev. J. M. Bacon. From the calen- 

 dar of the session 1904-1905, which comprises the usual day 

 and night classes for the preparation of candidates who enter 

 for the preliminary, intermediate and final examinations for 

 the London University Degrees in Science and Arts, we learn 

 that during the first term last year the class entries were, 

 evening, 3i6f); day, 5.S2. During the year sixty-four students 

 passed examinations of the University of London (seven with 

 honours), while other distinctions — scholarships, exhibitions, 

 prizes, certificates, and medals -were gained at the examina- 

 tions of various boards and societies : twelve students were 

 successful in the examinations for Assistant Surveyor of Taxes, 

 ten gained appointments as Assistant Examiners in the Patent 

 Office,andothersobtainedgoodappointments in other branches 

 of the Civil Service. Beyond this testimony to the practical 

 service of the " Birkbeck " to the persevering student, other 

 testimony must be borne to the excellent work it is doing in 

 spreading the systematic practical knowledge of science 

 among its widely distributed constituency. 



ASTRONOMICAL. 



ij^ical ( )l>ser\alory, 



vard 



ns, iiisll-tifnViilQp 



Mr. A. Law', 



WJts)Jv^- 



one at the tilt: 



AnnaLls of the Harvard College 

 Observatory. 



Two contributions have recently been issued under the aus- 

 ])ices of Harvard College. The first of these is the volume for 

 1901 and 1902 of the I?lue Hill M 

 and the expense of its public;iAjljn oiiiy 

 College, all the expenses of thealfcervyig stat 

 and investigations being borni^oy t'fifllljj/ 

 rence Rotcli. In addition to ni.iint.iroiiig tl 

 tions -ind automatic records at three station^ 

 Hill Observ.itory itself, a second -ftLJhc lia&^fyfa^^ (irelt 

 Blue Hill, and a third at the Neponsel^.flliiy-^rs^'eral inves- 

 tigations were undertaken, chief amongst which *.aP(ft<.'lE^- 

 ploration of the air with kites. Mr. Rotch is the American 

 member of the International Conmiittee for Scientific Aero- 

 nautics, and as far as possible flew his kites on the specified 

 international days, and when flights were not made on these 

 days, it was due to lack of wind at the ground, as a velocity 

 of at least six metres per second is required. If it is desired 

 to certainly fly a kite on any particular day, Mr. Rotch advises 

 the instalment of the apparatus on a steamer, which by creating 

 a wind through its motion will enable a sufficient current of 

 air to raise the kite. He advises by this means an investiga- 

 tion of the meteorological conditions above the trade- wind and 

 doldrums. Other investigations have also been conducted on 

 the audibility under various weather conditions, at Blue Hill ; 

 of the effect of weather conditions on the optical refraction of 

 the lower atmospheric strata ; and of the electrification of the 

 air and the quantity of carbon dioxide contained in it. These 

 last measurements seem to indicate that there are two maxima 

 of potential during the day, which are not always well defined, 

 and sometimes merge into one, occurring about noon or a little 

 before, and in the majority of cases there is a steady fall of 

 potential from about z p.m. until late in the evening, when the 

 electrification seems to reach a constant and low value. 



The second contribution from Harvard College is the 

 determination by Mr. W'inslow Upton, during the year 1896-97, 

 of the position of the Arequipa station in Peru. Briefly it 

 results : — 



Latitude, — 16' 22' 28-0". 



Longitude, 4h. 46m. ii'73S. west of Greenwich. 



Height above sea-level, 2451 -4 metres — 8043 feet. 

 Harvard College itself issues its circular (No. 74) on variable 

 stars of long period, and urges that in such cases it is useless 

 for observers to employ Argelander's exact method of 

 sequences. As it is, when the measures made at different 

 observatories on the same night are comp.ired, they often 

 differ by half a magnitude or more, owing chiefly to the red 

 colour of most of the long-period stars. The resulting 

 magnitudes would be nearly as good if the observer would 

 merely state that the variable was surely brighter than one 

 star and fainter than that next it in the sequence, without 

 attempting to estimate grades. Considering the large number 

 of variables of which we have no current observations, our 

 knowledge of their variations could thus be greatly and easily 

 increased. 



» * » 



Bulletins of the Lowell Observatory. 



A numlier of interesting bulletins (Nos. 9-13) have arrived 

 from the Lowell Observatory, and indicate the varied and 

 valuable researches that are carried on there. In No. g Mr. 

 Lowell gives a new determination of the position of the axis of 

 rotation of Mars, championing the direct and observational 



