An improved iron core magnet for general laboratory use, weighing two tons, has been designed and several units have been constructed. The design incorporates the desirable features of a number of earlier magnets and is engineered to give the optimum utility with minimum space and weight and with minimum attention by the operating personnel. A summary of test performance at 20 kw is given below. Operation at higher power levels will be described in Part II.11−in. diameter poles      5−in. gap10 kilogauss      2−in. gap17 kilogauss.534−in. diameter poles      2−in. gap23 kilogauss      1−in. gap30 kilogauss.1−in. diameter poles      1−in. gap32 kilogauss      12−in. gap37 kilogauss      14−in. gap42 kilogauss.