Abandoned technology

As new procedures and technology become available, the older technology is rapidly abandoned. A good example is methods for determining the size of DNA molecules. Prior to gel electrophoresis (agarose or polyacrylamide) DNA was sized with rate sedimentation in sucrose gradients, a slow and labor intensive technology requiring expensive instrumentation; prior to sucrose gradients, viscometry was used.
Aside from their historical interest, it is worth knowing about older technology as it may be useful to solve a particular problem.