1875.] Notices of Books. 105 
remarks on the estimation of tenths, on verniers, on the inser- 
tion of cross-hairs ; suspension by silk fibres ; temperature curve ; 
testing thermometers ; eccentricity of graduated circles; contour 
lines ; cleaning mercury; calibration by mercury; calibration by 
water; the cathetomer; the hook gauge; the spherometer; 
estimation of tenths of a second; rating chronometers; making 
weights: method of weighing; decanting gases, and their re- 
duction to standard temperature and pressure; standards of 
volume ; reading microscopes ; the dividing engine, and ruling 
scales. 
Successive sections then treat of the mechanics of solids; the 
mechanics of liquids and gases ; sound, and light. 
We strongly recommend this work to all physical students; 
and we will even say, that now so much attention is directed to 
subjects where physics and chemistry inosculate, its careful 
study will be useful to chemists. This is especially the case 
with the section on light. A second volume is announced, deal- 
ing with light and electricity. 
The Chemistry of Fermentation in the Process of Bread Making. 
By T. Karr Catitarp. London: Elliott Stock. 
THE author of this pamphlet does not accept the “ fungoid 
theory” of yeast. He holds that the ‘‘ yeast cells are simply 
vesicles of carbonic acid gas entangled in the elastic gluten;” 
and the growth of yeast he considers as ‘‘ nothing more than 
the conversion of fresh gluten into its own condition.” What, 
then, effects the conversion? ‘The constituents of bread, we 
are told, are ‘flour, yeast, potatoes, salt, and water.” The 
mention of potatoes would certainly have astonished our fore- 
fathers, and at the present day will astonish those numerous 
families in the north of England who bake for their own con- 
sumption, and who, be it remarked, produce bread less white 
and “ fluffy” than that of the London bakers, but sweeter, more 
digestible, and free from the tendency to turn sour. The use of 
potatoes in baking is certainly legalised by Act of Parliament, 
and cannot, therefore, be technically called an adulteration. 
That it is necessary the experience of generations has abun- 
dantly disproved. We are also told that flour containing little 
gluten is superior to samples in which this constituent is more 
plentiful! As a rule, we know that the wheats of cold climates 
are poor in nitrogenous matter, whilst those of Algeria, Hungary, 
Italy, and the Black Sea districts are rich. African wheat may 
contain twice as much gluten as Scotch. We grant that the 
last-mentioned may yield whiter bread, but we protest against 
colour being accepted as the standard of merit in any article of 
