The brood-cells, when their tenants have attained a certain age, are also covered with waxen lids, like the honey-cells; the lids differ a little, the latter being somewhat concave, the former convex. _The depth of the brood-cells_ of drones and working bees is about half an inch; _their diameter_ is more exact, that of the drone-cells being 3⅓ lines[AA], that of the workers 2⅗ lines. These, says Reaumur, are the invariable dimensions of all the cells, that ever were, or ever will be made. [Footnote AA: A line is the twelfth part of an inch.] From this uniform, unvarying diameter of the brood-cells, when completed, their use has been suggested, as an universal standard of measure, which would be understood, in all countries, to the end of time. "While heav'n-born Instinct bounds their measur'd view, From age to age, from Zembla to Peru, Their snow-white cells, the order'd artists frame, In size, in form, in symmetry the same." +Evans.+ CHAPTER XXXV. AN INQUIRY INTO THE SOURCE AND NATURE OF BEES-WAX. It has long been very generally and implicitly believed, that the yellow matter (in other words, the pollen or farina of flowers,) which bees visibly collect upon their thighs, is the prime constituent of wax, the material of the honey-comb. Even +Bonnet+ and +Reaumur+ were of this opinion. +Burler+, +Purchas+, +Rusden+ and +Thorley+ have argued against its identity with wax; and I trust that the observations and experiments which I am about to detail, will convince the dispassionate inquirer of the fallacy of this old opinion. In the first place, It is to be observed, that where no more comb can be built, as in old hives, the bees carry in the greatest quantity of this yellow matter. Secondly, That it differs materially from wax, the latter when examined between the fingers being adhesive, the former crumbly; the latter also liquefying on the application of heat, whilst the former burns to ashes. Thirdly, That the wax of new combs, from whatever source collected, is uniformly white; whereas the farina, as gathered by the bees, is always black, yellow, or red, agreeing in colour with the anther-dust of the flowers in blossom at the time of its collection. Moreover, the farina, after it has been stored in the cells, retains its original colour, whilst wax invariably changes, first to a yellow, and lastly to a blackish tint. Layers of different-coloured farina are generally found in the cells, if slit down; and every hive, at the season of deprivation, possesses a store of it.