XII. ELECTRON MICROSCOPY 401 



of universities are in the process of arranging graduate courses in 

 which formal training in electron microscopy -will be given. 



Another item of importance that often delays the application of 

 the electron microscope to a problem is its high cost. Electron 

 microscopes available at the present time vary in cost between 

 $7000 and $30,000. To introduce an item of this magnitude in 

 the budget of any scientific laboratory requires a very considerable 

 justification. In some cases it is relatively easy to find such justi- 

 fication. For instance, in industrial chemical laboratories there are 

 many cases on record in which the use of an electron microscope over 

 a relativelj'" short period has resulted in annual savings amounting 

 to many times the original cost of the instrument. In universities, 

 however, a somewhat different situation has existed. In practically 

 any school there are a number of departments that have problems 

 to which the electron microscope can be applied. While it is only 

 in the rare cases that an individual department is in the financial 

 position to purchase an electron microscope, it is usually possible 

 for the university as a whole to purchase an instrument, the expenses 

 being divided appropriately among the departments that make 

 use of it. Unfortunately, the co-ordination of research among various 

 departments of a university is not always such that this possiljility 

 is recognized. 



Another unfortunate situation that sometimes arises in finding 

 justification for the purchase of an electron microscope is that of 

 the laboratory which feels it has a need for an instrument but which 

 bases its decision not to buy one on a discouraging experience of a 

 similar laboratory at an earlier time, failing to realize that electron 

 microscopy is advancing at a very rapid rate and that most of the 

 major difficulties encountered by the early workers have since been 

 overcome. 



2. Electron Microscopes 



At the present time a number of different electron microscopes are 

 available throughout the world. In Europe, Philips in Holland, 

 Metropolitan \'ickers in England, and a number of other manu- 

 facturers have designed and either intend to produce or are already 

 producing electron microscopes. All these instruments have been 

 designed since the end of the war and relatively few of them are yet 

 in scientific laboratories. In America, only, has there been contin- 

 uous production of electron microscopes since before the war. These 



