60 The N.Z. Journal of Science and Technology. [Feb. 
and plants is stored up, and how it is again liberated when required. 
Mention was also made of the important part played by living organisms in 
the storage of the energy made use of by mankind in the complex activities 
of modern civilization. 
Wellington Philosophical Society. 
Two special meetings were held, on the 3rd and 5th December, when 
lectures were delivered by Dr. R. J. Tillyard, Macleay Fellow of the Linnean 
Society of New South Wales, on “ Neuropteroid Insects 55 and “ Fossil 
Insects.' 5 Dr. Tillyard gave a very clear presentation of the groups of 
insects, now recognized as orders, which formerly were included in the 
Linnean order of Neuroptera, and showed how the recent study of the 
Permian and Triassic insects of Australia had thrown light on the ancestry 
of insects and their classification. New Zealand abounds in primitive 
neuropteroid insects of the highest interest. The great development of May 
flies and caddis-flies has no doubt had much to do with the fine development 
of the introduced trout, which live mainly upon their larvae, and there is 
a danger that the balance of nature will be badly upset, and these insects 
totally destroyed in all streams and lakes in which the rainbow trout is 
present, unless steps are taken to limit severely the number of the trout. 
A Natural History and Field Club section of the society has been 
formed under the chairmanship of Professor H. B. Kirk, and a programme 
of excursions for the summer months has been arranged. 
REVIEWS AND ABSTRACTS. 
A New Theory of Plate Springs, by David Landau and Percy H. Parr. 
Journ. Franklin Inst ., vol. 185, No. 4 ; vol. 186, No. 6 ; vol. 187, 
Nos. 1 and 2 (April, December, 1918 ; January, February, 1919). 
A historical resume is given of the theory of plate springs, but the only 
work of importance found was that of M. Philips,* whose theory, however, 
was not in any way comparable with “our own researches.” The applica¬ 
tion of the results of sixteen years’ investigation to practice has resulted in 
springs which are a revelation even to those skilled in the art of spring¬ 
making. The new theory explains exactly everything that has needed 
explanation, and analyses fully and completely the behaviour and stress 
of every point in the spring. 
Any two successive leaves of a spring! when loaded will be in contact 
only at the buckle and at the extreme point of each leaf, except for odd 
cases of tapered leaves, which occur very seldom in practice. Considering 
the wth leaf, the deflection y n at the point is given by 
I 
EI m 2/„ = W„! 
w 
n — 1 
/ 2 7 
°n -1 b 
Vt-l\ . 
6 / ’ 
considering the (w-fT)th leaf, 
El + iy„ = w, 
n + L 
7 7 2 
L n +1 bi 
— ) — W — 
6 / n 6 
* Annates des Mines, 1852, I, 195. 
| See fig. 4 of article in this issue, “ Design of Laminated Springs,” p. 19. 
