The blowing process is also subject to wide variations of practice. The most important of these variations concerns the shape and dimensions of the cylinders. In English and Belgian works the dimensions of the cylinders are so chosen that the length of the cylinder constitutes the longest dimension of the finished sheet, the diameter of the cylinder forming the shorter dimension. In some parts of Germany, however, the practice is the reverse of this, the cylinders being blown shorter and much wider, so that the circumference of the cylinder constitutes the longest dimension of the finished sheet. It is, however, pretty generally recognised that the latter method has very serious disadvantages, although it is claimed that somewhat more perfect glass can be obtained by its means. For the production of a special variety of glass, known as “blown plate glass,” this method of blowing short wide cylinders is still adhered to. This is a very pure form of sheet-glass, blown into thick, small sheets which are subsequently ground and polished in the same manner as plate-glass. Here the great thickness of glass required seems to render the blowing of long cylinders very difficult, and the other form is therefore adopted. On the other hand, English patent plate-glass, which is made by grinding and polishing the best quality of ordinary sheet-glass, is made from glass blown into long narrow cylinders in the manner described in detail above. The process of blowing described above is capable, with slight modifications, of yielding glass with surfaces other than the plain smooth face of ordinary sheet-glass. Thus fluted and “muffled” glass are produced in a very similar manner to that described above for ordinary sheet, except that the fluting or the irregular surface markings which constitute the peculiarities of these two varieties of glass, are impressed upon the surface of the cylinder at an early stage in the process.