
774 NATURE [JUNE 9, 1923 
Some relation of this kind was surmised by Faraday, | of molecules ‘rigidly’ attached to each other as in a 
who wrote: “ My impression has been that there | solid, and in part of molecules which are relatively 
was a certain temperature for each body (well known 
in the case of iron) beneath which it was magnetic, 
but above which it lost all power; and further, 
there was some relation between this point of tem- 
perature and the intensity of magnetic force which 
the body when reduced beneath it could acquire” 
(Phil. Mag., 1836, vol. iii. p. 177). 
J. R. ASHwortTH. 
55 Wing Street South, Rochdale, 
May 5. 

A Puzzle Paper Band. 
Some thirty or forty years ago geometricians were 
much interested in the endless band of paper to which 
one half twist had been given before joining the ends. 
This gave the figure having only one surface and one 
edge. At that time those who studied this figure 
were so obsessed with the consequence of cutting 
down the middle line of such a band or of a band 
with two or more half twists that I believe no one 
noticed the result which I wish now to describe. It 
is the doubling up in a proper manner of an endless 
band to which four half twists have been given so as 
to produce the endless band first described but of 
double thickness. The first band is shown at A, 
as an endless belt connecting two crossed shafts 
for which, as is well known, jit is 
exactly fitted. B shows the band 
with the four half twists all on one 
side in the form of two complete 
loops, and to be uniform with the 
other it is shown as an open band 
connecting two parallel shafts. The 
only object of putting in the shafts 
and pulleys is to assist the perspec- 
tive. They are not wanted in making 
the experiment. Now if B, which 
appears sufficiently uncompromising, 
is folded up properly it becomes A 
but of double thickness. 
I used this doubled A for a time as a record sheet 
for my recording calorimeter, for, having a head-room 
to work in of four feet and a movement of paper 
of six inches a day, I was able in this way to obtain 
a continuous record for 32 days on one side of the 
paper only. This is superseded now by a more 
convenient arrangement. 
It may be worth while to add that while lying 
awake one night I visualised A in two thicknesses 
and saw it to be what I wanted, and the next day 
I found it all right. What I did not visualise was 
the puzzle that it is to fold up B into an A of double 
thickness, and that it makes a first-class parlour 
puzzle game. It has this further advantage that a 
number may be made, some with right-hand and 
some with left-hand twists, so that any preliminary 
success gained on one may make the other seem the 
more difficult. The band should be not less than 50 
times as long as it is wide. 
Of the four half twists two are easily seen in the 
finished double thickness band, for each thickness 
has one half twist; it is amusing to find out where 
the other two have gone. C. Ve Bays; 


The Viscosity of Liquids. 
In Nature for May 5, p. 600, Prof. C. V. Raman 
writes: “‘ I have suggested that the viscosity of liquids 
and its variation with temperature may be explained 
on the hypothesis that the liquid state of aggregation 
is composite in character ; that is, is composed in part 
NO. 2797, VOL. II1| 


ae as in the gaseous state (NATURE, April 21, 
P. 532).”” 
The above hypothesis was suggested by me in a 
paper which appeared in the PhilyMag. for Feb. 1888, 
p- 156. In solids the atoms or molecules, in normal 
conditions, are, in the majority of instances, adhering 
to each other, and if, owing to vibratory movements 
within the mass, the adhesion should be broken any- 
where, the same bond is quickly restored if the mass 
be only moderately strained. If, however, the mass 
should be in a state of considerable strain, broken 
bonds may make new attachments, and the solid be 
permanently deformed. In the case of liquids, 
although the majority of the molecules are bonded by 
chemical forces, a number, depending upon the tem- 
perature, etc., are continually breaking bond, even in 
the absence of strain, but, instead of again remaking 
the original bonds, they may form fresh bonds. In 
the paper already quoted, p. 160, [remark : “‘ Gravity 
may, therefore, give rise to a slow but continuous 
change of form in an elastic substance in the interior 
of which liquefaction and resolidification are con- 
stantly going on.” The theory, particularly as 
regards ice, was afterwards developed in some detail, 
and I should like to invite attention to a paper on 
“The Viscosity of Ice,’’ Proc. Roy. Soc. A, vol. 81, 
1908, p. 250. 
Irving Langmuir (Jour. Amer. Chem. Soc., vol. 
xxxix., Sept. 1917, p. 1858) also advances the same 
idea. He remarks: ‘‘ The mobility of a liquid is thus 
due to a shifting of the relative positions of atoms 
which are all chemically combined with each other.” 
R. M. DEELEY. 
Tintagil, Kew Gardens Road, Kew, Surrey, 
May 14. 

Perseid Meteors in July 1592. 
In Nature of November 18, 1922 (vol. 110, p. 667), 
| there appeared a letter from Mr. H. Beveridge, - 
directing attention to a statement by Abul Fazl that 
“on the 27th day of Tir O.S., which might correspond 
to about July 28, 1592, three hundred little stars or 
pieces of stars (sitavacha) were seen traversing the 
heavens from west to east.’’ The date, Tir 27, belongs 
to the Tarikh-i Ilahi, or Divine Era, which was used 
by Abal Fazl, and must not be confounded with other 
calendars in which the same month names occur. 
In a study assisted by Mr. Beveridge’s courtesy I 
have examined a large number of dates belonging to 
this era, and I find that each year was made to begin 
at the sunset following the vernal equinox, and, so far 
as the dates can be tested by the days of the week or 
by an astronomical phenomenon, each month would 
appear to have been made to begin at the sunset 
following the entrance of the sun into a sign of the 
zodiac. There is one instance, however, where a 
month is made to begin one day earlier than it should 
according to this rule. According to this rule Tir 27 
should begin at the twenty-seventh sunset after the 
summer solstice, which in the year 1592 would be 
on July 7 of the Julian calendar or July 17 of the 
Gregorian calendar, and I infer that the meteors were 
observed on the night of July 17-18 of the Gregorian 
calendar. There is no reason to suspect an error of 
more than one day in this date. In his translation of 
Abil Fazl’s Akbarnama Mr. Beveridge identified Tir 
24 of that year with July 4 of the Julian calendar, and 
I take it that July 28 in his letter to NATURE was a 
lapsus calamt. 
In the Observatory for May 1923, p. 169, Mr. W. F. 
