January 4, 19 12] 



NATURE 



129 



When, a few years ago, it became evident that the ques- 

 tion of afforesting a portion of the British Isles had 

 developed into a matter of considerable public importance, 

 Kdinburgh again led the way, and instituted a degree of 

 13. Sc. in forestry and appointed lecturers to deliver the 

 Special courses which the forestry student is required to 

 take, such as forest botany, forest chemistry, forest 

 engineering, and forest entomology. 



The University did not, however, rest content with this. 

 The demands made upon the resources of the department 

 led to the recognition of the fact that provision was re- 

 quired for three additional objects : — 



(i) A forest garden, including an area for the experi- 

 mental formation of woods. 



(2) Extensions of the present museum and the provision 

 of laboratories. 



C3) Additional lecturers on the University forestry staff. 

 During the past year undivided attention has been 

 devoted, in collaboration with the Edinburgh and East of 

 Scotland Agricultural College, towards the attainrrient of 

 these objects. 



The Development Commissioners were approached bv the 

 University Court and the governors of the .Agricultural 

 College, and their applications were received with sympa- 

 thetic consideration by the Commissioners, and have been 

 accorded generous treatment. 



A sum of money has been promised annually for a 

 period of years for the rent and upkeep of a forest garden 

 and area of experimental plantations. This sum has been 

 promised conjointly to the University and College, and the 

 authorities of these two institutions have appointed a joint 

 committee to supervise the management of the area. 



The Development Commissioners, recognising the urgent 

 need of additional room for the extension of the forestry 

 department within the University, its museums, and labora- 

 tories, have granted the University a sum of 4500Z. towards 

 the erection of a new forestry building, stipulating that 

 the University should provide "a similar sum. The Uni- 

 versity Court has undertaken to provide this amount, or a 

 larger one should it be required. The Development Com- 

 missioners have also made a grant of 2000Z. towards the 

 equipment of the museums and laboratories, the money to 

 be spent during the next five years. The Commissioners 

 have promised to consider a further provision for this 

 object should such be required at the end of this period. 

 It is expected that the erection of the buildings will be 

 commenced in the coming year. 



The instruction in forestry proper for the degree will 

 remain in the University, and with the object of supple- 

 menting the staff of the department the Development Com- 

 missioners have granted a sum of 2500Z. (500/. a vear for 

 five years) as a provision for the salaries of an additional 

 lecturer and for an assistant in the forestry department. 

 One of these gentlemen has been already appointed, and 

 the second will be shortly added to the staff. 



The above detailed explanation of the present position of 

 Edinburgh with regard to education in forestry will show 

 that both the University and Agricultural College have 

 Ljone thoroughly into the matter, and have determined that 

 very effort shall be made to give the best forestry education 

 possible alike to the student wishing to graduate in forestrv 

 and to the working forester and woodman who wishes 

 to improve his education by following the simpler forestry 

 courses delivered at the Agricultural College. 



T^.ST5 OV PROPELLERS FOR FLYING- 

 MACHINES. 

 A SERIES of important and valuable experiments arc 

 being carried out at Chalais-Meudon by MM. 

 Legrand and Gaudard with the object of testing propellers, 

 while actually in u.se, on a flying machine, and of studying 

 the action of the air on planes in flight. The machine used 

 is a biplane specially built for the purpose at the labora- 

 tory ; the propeller in front is run off a 60 horse-power 

 Renault motor ; the planes are staggered ; and the total 

 weight, including the pilot, is 780 kilograms. 



In order to study the action of the air on the propeller 



and planes of a machine in horizontal flight, the following 



details must be known :— (i) the thrust of the propeller ; 



(2) the speed of rotation of the propeller-blade or of the 



NO. 2201, VOL. 88] 



motor ; (3) the actual speed of the aeroplane as it would be 

 in calm air ; and (4) the angle of incidence of the machine. 

 The way employed in these experiments is to take simul- 

 taneous and instantaneous readings of all these details by 

 the aid of special apparatus connected electrically, so that 

 the pilot can choose his own moment and take the readings 

 by pressing a button. The method of obtaining the angle 

 of incidence and the speed of the machine is particularly 

 ingenious. It consists of photographing the angle indicator 

 — a pendulum moving in oil — and the manometer recording 

 the pressure of the air-flow. In this way observers are not 

 required, and the factor of personal error is eliminated. 



Experiments have already been made with two pro- 

 pellers, A and B, A having a diameter of 265 metres and 

 a pitch of 2-10 metres, and B a diameter of 285 metres 

 and a pitch of 170 metres. The motor gave out 62 horse- 

 power at 1800 revolutions, which was its normal speed, 

 but in the case of A the revolutions in flight went up to 

 1870, and in B to 1980. It was found that a considerable 

 deformation of both propellers took place during flight by 

 which the pitch was reduced equally on both blades of A 

 by 350 mm., but unequally on B to the extent of 350 mm. 

 on one and 270 mm. on the other, so that when B was 

 used considerable vibrations were observed. 



At a speed of 17 metres per second propeller A gave out 

 168 kilograms thrust when the angle of incidence was 

 9° 45', and at a speed of 16 metres, when the angle of 

 incidence was 10° 15', the thrust was 160 kilograms. B, 

 on the other hand, at a speed of 15 metres, when the angle 

 was 11°, only gave a thrust of 153 kilograms. 



In static tests, A gave 225 kilograms and B 245 kilo- 

 grams. The experimenters, as an outcome of these pre- 

 liminary tests, state that many of the modern propellers 

 in use have too small a relation between their pitch and 

 diameter to be really efficient. 



Lieut. Saunier piloted the machine on its trials, making 

 only short, straight flights when there was practically no 

 wind. 



NEW MICROSCOPIC OBJECTIVES AND 

 ACCESSORIES. 



\A7 E have received from Messrs. Angus, agents for R. 



** Winkel, of Gottingen, some of his later productions 

 which include special features. 



With regard to the objectives, they have been examined 

 and reported on by Mr. E. M. Nelson,' whose authority 

 on such matters is second to none, so we may content our- 

 selves by referring to his statements relating to the special 

 colour correction of the achromats which Winkel employs, 

 especially as he introduces a history of the changes made 

 in these corrections which is of great interest. 



" Before the introduction of Jena glass, the outstanding 

 secondary spectrum of the old English archromat consisted 

 of claret, or port-red, and apple-green colours. This • was 

 always looked for by experts, and its presence was thought 

 to denote perfect correction. .About 1870 (or a year or so> 

 later) Tolles, in America, altered the correction, and pro- 

 duced some very fine object-glasses with a flaring bright 

 red, or crimson, spectrum. I well remember seeing a 

 Podura scale shown with one of these glasses, a very 

 brilliant lens, and a strong diatom resolvcr ; the exclama- 

 tion marks shone out like rubies, whereas if they had been 

 viewed through an English objective of that date (Lister 

 formula) the exclamation marks would have been seen with 

 a more purple tint, something like an amethyst. 



" About 1886, when Jena glass was introduced, an 

 entirely new set of phenomena appeared ; pale glasses, and 

 those which gave decidedly bluish tints— which any expert 

 of those days would have unhesitatingly condemned — were 

 found to be not only strong diatom resolvcrs, but also to 

 give sharp and bright pictures. For a time, experts, until 

 they had learnt the effect of the reduction of the secondare 

 spectrum by these new corrections, were all at sea, and 

 did nol know where they were. 



" To-dav, there is in my cabinet one of these Jena glass 



semi-apochromats which has such a violent purple 



s(><()ii(l;it V sDcctrum that it can be seen even when a pe.i- 



i^s is used, a more monochromatic fluid 



Joum. R. Micr. Soc., 191 1, pp. 45>-5»- 



