March 9, 1871] 

NATURE 
379 


heat a grain of zinc consumed equals 158 foot pounds, if 
« = pounds raised a foot high per consumption of a grain of zinc 
in the battery, — 
(a = 4) 158 
a 
z= 
Hence the authors draw the conclusion :—‘ Therefore when 5 
vanishes, or becomes infinitely small, the economical duty is a 
maximum.’ Certainly this is a most startling restilt; that the 
maximum of work should be done when no zinc at all is con- 
sumed.” The last sentence is a mis-statement of the conclusions 
of Joule and Scoresby’s paper, in which (Philosophical Magazine, 
vol. 28, p. 451) it is stated that ‘‘the economical duty will be a 
maximum when é vanishes or becomes infinitely small in com- 
parison with a In this case « = 158, while the power of the 
engine will become infinitely small with regard to work performed 
ina given time.” Comparing the phrases ‘‘economical duty” 
and ‘*maximum of work,” as he uses them, he evidently confuses 
the duty of an engine with the whole work done by it. A little 
further on we have—‘‘ They calculate the maximum theofretical 
power of a grain of zinc to be 158 foot pounds, and yet using per- 
manent magnets, which, by their own statement, were so badly 
constructed as to have only a quarter the power they ought to 
have had, with the poles of the electromagnets never approaching 
the permanent magnets nearer than 4} of an inch (and what an 
enormous loss is incurred here!); with an engine constructed 
almost at haphazard, and with scarcely a consideration of the best 
principles or of the most advantageous construction of such 
engines, they actually obtained a result of 102°9 foot pounds out 
of a calculated theoretical maximum of 158. With a little care 
and consideration, I do not hesitate to say the duty per grain of 
zinc might easily have been increased tenfold.” It is hardly 
credible, but the above looks very like a confusion between Force 
and Work! The author seems to assume that if the forces in 
operation in an engine are greater, that the engine will necessarily 
produce more work from the same quantity of fuel. In these ex- 
periments the quantity of zinc (e—4) used to produce work W 
is observed; if the engine was made more powerful, if the 
permanent magnets were four times as strong, and the electro- 
magnets passed } of an inch from them, doubtless W would be 
greater, but so also would (a@—4), and it does not follow that 
with which we are concerned would be at all changed. 

Ww 
(2-4) 
What becomes then of the dogmatic assertion that the duty ofagrain 
of zinc could be increased tenfold ? Now let us turn to the paper in 
the Quarterly Journal. Here we may find enough in one article for 
our present purpose, taking chap. ii. art. 2, —‘‘ Why are we forced 
to suppose . . . . . . that the same amount of fuel produces the 
same amount of energy, whether it is consumed in the steam- 
engine, the horse... .. . the gnat? At any rate, we may 
observe that the very phrase is certainly a misnomer, and a mis- 
nomer of such a kind as to havea fatal effect in producing a false 
conception of things. For mechanical energy just as often pro- 
duces cold as heat ; it may produce either heat or cold, or neither. 
In fact, as a general rule, though with notable exceptions, every 
pushing or compressing force produces heat, and every pulling or 
expanding force cold. Place a weight ona pillar, and the weight 
produces heat in the pillar; hang it on a wire and it cools the 
wire. In exactly the same way, in a fire-syringe use force to 
press down the piston, it produces heat—heat enough to kindle 
tinder ; but use the same force to pull up the piston, and it pro- 
duces cold.” Surely this is enough to show that the author’s 
notions of what he is attacking are, to say the least of it, shallow ; 
for what he quotes as paradoxes are simple deductions from the 
two laws of Thermodynamics. That a wire is cooled by stretch- 
ing follows from the fact that heat expands it. In the case of the 
fire-syringe the case is simpler. The working body is the air in 
the syringe; on pulling up the piston this air does work, and 
therefore uses up heat and is cooled. Mr. Highton seems to 
imagine that because the arm of the experimenter does work, it 
is done on the air in the syringe, whereas this column of air and 
the observer are really co-workers in raising the air external to 
the cylinder. To point out all the fallacies of these papers in 
detail would take too much of your time. My object was to show 
that if the Quarterly Fournal of Science and the Chemical News 
are to represent scientific opinion with any degree of truth, they 
would do well to use a little discretion as to what they print.— 
“* Remarks on Mr. Spence’s Experiments on the Effects of Cold 
on the strength of Cast Iron,” by Joseph Baxendell, F.R.A.S. 

This was in reply to an assertion made by Mr. Spence the pre- 
vious week that ‘‘he had so much confidence in the experiments 
then detailed, that he had no hesitation in giving it as an ascer- 
tained law that a specimen of cast iron having at 70° F. a given 
power of resistance to transverse strain will, on its temperature 
being reduced to zero, have that power increased by 3 per cent.” 
Taking all the experiments on the effect of cold on iron which 
have yet been brought before the Society, they can only be 
regarded as indicating that if any effect at all is produced, it is more 
apparent on iron of good quality than on inferior iron, but that its 
amount is so small as to be wholly inadequate to account for the 
railway and other accidents which have been attributed to it.— 
‘Further Observations on the Strength of Garden Nails,” 
by J. P. Joule, F.R.S., &c, Since communicating the paper 
on the Alleged Influence of Cold in giving brittleness to 
Iron, I have collated the results with cast-iron nails in order to 
show the range of strength in such specimens : 
Height of Fall Percentage of 
of Hamnier. Fractures. 
2 inches . . : EKO 
2 ' . 5 - eo 
Ey an . ‘ F . enOIZ5 
34 95 OR a SN ast, ILS 
4a. c ‘ 0 . a Be) 
44», He AMA 3 OFA 
53 ” a \! 37°5 
OR sy < : 5 wae 
ve oo : . . : 65°5 
amen 5 . . . 3 eR 
83 ” \s C ° oe 7s) 
10 28 
” . . . . 
I chose the garden nails for experiment after some thought, as 
presenting a marked variety of metal in contrast with the iron 
and steel wire, tempered and untempered. I did not expect them 
to possess great strength, but having found them to require a 
heavier blow than I expected to fracture them, I have had the 
curiosity to make some experiments on them which may be 
interesting to the Society. I took pairs of the nails, placed them 
head to point parallel to each other, so that pressure applied in 
the middle by pincers sufficiently forcibly would fracture one of 
them. Paper slips were pasted on the edges of the nails, and 
their distances asunder measured by a microscope with micro- 
meter eyepiece divided by lines corresponding to <4, of an inch. 
Weights were gradually added to the lever of one arm of the 
pincers until fracture took place, which was always accompanied 
with a sharp report. The observed deflection or bending of the 
nails was taken continuously as the weights were laid on, and 
the calculation of what it would have been at the moment of 
rupture taken from the immediately preceding observations. The 
amount of deflection was almost exactly proportional to the weight 
laid on in each experiment. 

No. of _Lengthof Breadth of Depth of Breaking 
Experi- Nailbetween _Nail in Nail at Deflection. Weight. 
ment. Supports. Fracture. Fracture. Ibs. 
I 1'05 o'13 O'127 ‘0062 145°5 
2 I'l O'lI4 O'125 0067 141 
3 Ist "120 O'LI5 0090 171 
4 108 Ovlll o"106 "0973 142°5 
5 I'I2 O'122 O°145 "0095 189 
6 1°06 0138 0°120 "0087 184°5 
7 108 O'150 ors "0095 201 
Average 1084 0°1264 O°1223 0082 167°8 
If we compare the above with Mr. Brockbank’s experiments, 
we shall find, approximately, on reducing them to the dimen- 
sions he adopted, viz., three feet between supports and one inch 
section :— 
Breaking weight. Deflection. 
Mr. Brockbank’s, with large bars... 860°7 "740 
My own, with nails... ee + 2673" 1106 
The metal, in the form I used it, was therefore more than 
three times as strong as that of the large bars to resist a com- 
pressing and tensile force, while its extent of spring at the break- 
ing weight was half as much again. Therefore, so far from 
being of inferior quality, it would sustain a very much heavier 
blow without fracture. —‘‘ On the Action of Sulphurous Acid on 
Phosphates,” by Dr. B. W. Gerland. 
