A dissolving apparatus has a cylindrical tubular container closed at both ends with its center axis being inclined to the horizon. The first member and second member are joined by providing a raw material for the joining material between the first and second members and heat treating the raw material at a temperature of 1730\xb0 C. The varying cross-sectional configurations of the different fiber forms causes the fiber forms to have different levels of spreadability and frictional resistance to movement of the fiber. Each detector group includes a blue-sensitive detector layer at an n-type layer at the surface of the semiconductor, a green-sensitive detector layer at an n-type layer deeper in the semiconductor, and a red-sensitive detector layer at the n-type layer deepest in the semiconductor. In use, the elongated and compressed positions of the bellows are each no more than 5 degrees off the center resting position thereby reducing stress on the bellows.