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The congruences of a finite sectionally complemented lattice 
$L$ are not necessarily uniform (any two congruence classes of a congruence are of the same size). To measure how far a congruence 
$\Theta $ of $L$ is from being uniform, we introduce Spec $\Theta $, the spectrum of $\Theta $, the family of cardinalities of the congruence classes of $\Theta $. A typical result of this paper characterizes the spectrum 
$S=({{m}_{j}}|j<n)$ of a nontrivial congruence $\Theta $ with the following two properties:
$$({{S}_{1}})\,\,\,\,2\le n\,\,\text{and }n\ne 3.\,\,\,\,$$
$$({{S}_{2}})\,\,\,2\le {{m}_{j}}\,\,\text{and}\,\,{{m}_{j}}\ne 3,\,\,\,\text{for}\,\text{all}\,j<n.$$
