The rates of postage were modified in 1699, and again in 1712; but as the old rates were retained as the basis of both revisions, the charges remained for fifty years substantially unchanged. A letter from Berlin to Hamburg now cost 2-1/2 groschen, to Bremen 3 groschen, to Dresden 2 groschen, to Frankfort-on-Main 3 groschen, and so on. During the next fifty years prices were gradually, but steadily, rising in Prussia. The Seven Years' War produced a sudden and very considerable rise in the prices of all agricultural products. And not only did the purchasing power of money fall owing to the scarcity and high price of provisions, but its value also decreased through depreciation.[232] The cost of conducting the postal service rose correspondingly, and the financial difficulties were increased owing to the falling off of traffic consequent on the war. At the end of 1761 the King was asked to agree to a contribution in aid, but assistance was not forthcoming. Something had to be done; and on the 27th January 1762, in common with the general increase of taxation, the rates for parcels and for value letters were increased 100 per cent.; the travelling post rates, which varied from 3 to 4 groschen per mile, were increased by 1 groschen per mile; and the fees for guides, which were about 6 groschen per station, by about 2 groschen per station. The letter rate remained unchanged.[233] In the early part of 1766 a new tariff was introduced. The rates for parcels fixed in 1762 were maintained, and new and higher rates for letters were introduced. The increase in the general rates varied from about 15 per cent. to about 50 per cent. The minimum, which for letters passing between many neighbouring places had formerly been only 6 pfennigs, was increased to 1 groschen. The raising of the rate led to a large amount of fraud, and caused much public inconvenience. The revenue did, indeed, increase in the first year quite appreciably; but in the second and third years, instead of the normal yearly increase, there was a notable decrease. Complaints against the new rates were widespread, and it was alleged that the increased charges embarrassed commerce. In 1770 the rates for heavy letters, printed matter, and documents were reduced again to those of 1712. The rates had previously been based on a variety of considerations,[234] but this miscellaneous basis was now put aside and a uniform system established, the same letter rate being applied throughout the State. The coinage edict of 1821, by which the thaler was divided into 30 silver groschen instead of 24 groschen as previously, made necessary an alteration of the postage charges, and amended rates were established on the 1st January 1822. No account was taken of a less amount than a half-groschen, and odd amounts were reckoned at the next half-groschen above, with the result that in certain cases the rate became higher than formerly.