"Let Q... be the quantity of heat which must be imparted to a body during its passage... from one condition to another, any heat withdrawn from the body being... [a] negative quantity... Q may be divided into three parts... the first... in increasing the heat... in the body, the second in producing the interior [work]... the third in producing the exterior work. ...[T]he second ...[and] first... together... represented by... function U... [are] completely determined by the initial and final states of the body. The third part... the equivalent of exterior work, can, like this work itself, only be determined when the precise manner in which the changes of condition took place is known. If W be the quantity of exterior work, and A the equivalent of heat for the unit of work, the value of the third part will be A · W, and the first fundamental theorem will be..."