fe 233] 
XXII. Eprrortat Nore. 
HAVE received from Lord Blythswood a letter of date 
Jan. 23, with a specimen of cambric rendered thoroughly 
brittle or rotten by exposure for.about three days to radium 
bromide. He had put a little circle of cambric in place of 
the circular sheet of mica which is commonly used to cover 
the cavity containing radium bromide in the little receptacle 
in which it is usually sold. The cambric is quite broken 
away, leaving an irregularly shaped hole of about 38 mm. 
greatest diameter in the place which was directly exposed to 
the radium. This is certainly a very interesting and, I 
believe, important discovery. Lord Blythswood found the 
same result in several other trials with exposures of two or 
three days. 
KELVIN. 
Largs, Jan. 26, 1904. 


XXIII. Notices respecting New Books. 
A Handbook for the Electrical Laboratory and Testing Room. 
Vol. Il. By J. A. Fuemine, W.A., D.Sc. FAS. London: 
“The Electrician” Printing and Publishing Company, Limited. 
1993. Pp. vii+622. 
JOTHING could better illustrate Dr. Fleming’s tremendous 
activity as a writer of text-books than the appearance of this 
second volume of his ‘ Handbook’ within something like a year 
from the date of publication of Vol. I. The compilation of this 
second volume must have involved a very large amount of labour, 
and the very full references to original sources show that the 
author has spared no pains to make his treatise of as encyclopedic 
a nature as possible. 
The book is divided into five chapters. In Chapter I. we have 
an account of the measurement of electric quantity and energy. 
We are heartily glad to see Dr. Fleming’s strong condemnation of 
ballistic galvanometers of the needle type. In connexion with 
the damping correction of a ballistic galvanometer, attention may 
be drawn to the extremely clumsy form, sanctioned, no doubt, by 
long usage, in which this correction is applied. We are sorry to 
see the time-honoured treatment reproduced by Dr. Fleming. The 
student is told, by teachers and text-books alike, to find the 
“logarithmic decrement” A of the galvanometer, and then to 
correct the “throws” by multiplying them by 1+ ; . Now this 
A 
mysterious 1+ ; is simply an approximation to ¢?, being, in fact, 
Phil. Mag. 8. 6. Vol. 7. No. 38. Feb. 1904. R 
