86 MEASUKIiMENT OF RAINFALL. 



being dealt with, and, as Mv. F. E. Kanthack, M.l.C.E. pointed 

 out in his address to the First South African Irrigation Congress, 

 in 1909, that generah'sation in rainfall is not much use for prac- 

 tical purposes; this is undoubtedly true, not only for tlie Irriga- 

 tion Engineer, but in every department of engineering into which 

 the question enters. 



When it is considered that large sums of money have been 

 spent in the past— and much of it on guess work — and that still 

 larger sums have to be spent in the future for accommodating the 

 rainfall in South Africa, the author, after years of personal con- 

 tact with the problem, is of opinion that what is required is a 

 more exact measurement of rainfall in every district in South 

 Africa. 



Lightning Conductors at St. Paul s Cathe- 

 dral.— The recent installation ot new lightning conductors at 

 St. Paul's led to the discover}- that a portion of oiie of the 

 original iion l)av conductors, which, was erected under the super- 

 intendence of Benjamin Franklin himself about 140 years ago. 

 was still in position and in a good state of preservation. When 

 lightning conductors were originally empkyed, they were termed 

 *' Franklin rods," and a warm controversy arose at the time as to 

 whether they should terminate in points or balls. King George III 

 was a hrm believer in ball terminals, and the advocacy of points 

 by the President of the Royal Society brought about his resigna- 

 tion. 



Amphibian Poison. — Prcf. J. Arthur Thomson writes, 

 in a recent number of Knowlrcio;,' : " It is well known that the 

 defenceless amphibians — toads, frogs, newts, salamanders, anrl 

 the like — are protected by a poisonous secretion formed by skin 

 glan(E. The phr\-nin of the toad has been often experimented 

 with, and is a powerful poisv;)n. Wadame Phisalix has recently 

 found thai injections of a modificatic-n of amphibian poison- will 

 immunise an animal. (\.c.. rabbit or guinea-pig. against a strong 

 dose of the same poison. This is what might have been expected 

 from analogous cases. Cut the further i)oint is of nnich interest 

 — that animals immunised against amphibian poison are also im- 

 munised against the poison of the viper." 



Volcanic Dust and Climatic Change.— In a 



paper nubHshed in the BiiUctiii of the Mount Weather Obsenv- 

 tory, \1 fi] 1-3-1- Prof. W. J. Humphreys discusses the various 

 factors in the production of climatic change, and particularly the 

 profound changes resulting in the glaciation of the ice-ages. He 

 considers that "the presence of volcanic dust in the upper atmo- 

 sphere, is an important factor, wdiich decreases the intensity of 

 solar radiaticn in the lower atmosphere, and therefore the tem- 

 perature of the earth, .^n elYect such as this he traces Imck as 

 far as 1750. These changes of temi)erature, though small in 

 absolute magnitude, are of^gi'eat importance, seeing that a varia- 

 tion of only \. 26'' F. has been known to delay the maturing of tho 

 . Mauritius sugar cane crop by a whole year. 



