GENERAL NOTES. | 421 
are named in order, and each name is followed by that of its 
author, the publication in which it was originally described, and 
its date. Then follows a list of the various parts of Australia in 
which the plant is known to occur, and lastly a reference to the 
volume and page of Bentham’s “Flora Australiensis” or 
Mueller’s “Fragmenta” in which it is described. The work 
should be in the hands of every colonial botanist. It is remark- 
ably well printed. 
FORMUL& FOR SCREW POWER.—Mr. A. Y. Ross, of Gisborne, 
writes to us that, having found no theoretical formula for screw 
power in any works on Mechanics which gave results exactly in 
accordance with those obtained in practice, he has been led to 
institute a series of experiments with the view of obviating this 
defect. From these he has drawn up the following empirical 
formulse, which will, he claims, solve accurately any of those 
problems in screw power which the practical engineer constantly 
meets with. We regret that we cannot shew the illustration 
which accompanies Mr. Ross’s communication. 
FORMULA. 
W = Weight to be raised. 
P = Pressure at end of lever necessary to raise W. 
L = Length of lever required, diameter of screw as unit. 
C = .36 Coefficient of friction, Iron upon Iron, &c., see Table.* 
R = Pitch or rise of thread compared with its length. 
2 xe EP W x (C+ R) Wx (Cee RR) =oP 
nee TS yp Pe ee py SE eee 
GC - R PTE) Ngee el ok | 2P 
’ 
TONGARIRO.—After an interval of thirteen years of com- 
parative quiescence this volcano has again broken out into 
violent eruption. Tauranga and Napier.telegrams of 26th April 
inform us that the mountain was emitting an immense column 
of black smoke, which continued for several hours. No fire 
could be seen. Owing to the cloudy weather the observations 
appear to have been very imperfect. No earthquake shocks 
were felt. SS 
PROFESSOR WALKER, recently appointed to the Chair of 
Mathematics and Mathematical Physics in Auckland University, 
was drowned while out boating in Auckland Harbour yesterday 
(1st May). The unfortunate gentleman was out in a small boat 
* Coefficient of friction varies slightly according to weight per square inch, 
unguents used, and the material the screw is made of. 
COEFHKICIENT OF FRICTION TABLE, BY MR. G. RENNIE, 
Pressure per square Wrought Iron upon Wrought [ron upon Brass upon Cast 
_ inch, Wrought Iron. Cast Iron. Iron. 
I cwt. »250 2275 225 
2 ae 292 .219 
3 312 »333 a-Hiiils 
4 -395 365 208 
— 4.66 -409 366 223 
