[311.] Problema. XIX. Triangulum E S F, Leida, Gouda, Rotterodamum.

[312.] Problema XX. Triangulum E S V. Leida, Vltrajectum, Gouda.

[313.] Problema XXI. Triangulum E R V, connectens Trajectum, Leidam, Dordracum.

[314.] Problema. XXII. Triangulum E M V. Leida, Oudewatera, Vltrajectum.

[315.] Problema XXIII. Triangulum E M S. Leidam, Oudewateram & Gou-dam connectens.

[316.] Problema XXIV. In Triangulo A E I Haga, Leida, Harlemum.

[317.] Problema XXV. Tab. XV. fig. 15. Diſtantia inter Harlemum & Leidam alio modo quæſita in Triangulo I A E.

[318.] Problema XXVI. Tab. XVI. Triangulum O E V, Amſtelodamum, Leida, Vltrajectum.

[319.] Problema XXVII. Triangulum E I V, Leida, Harlemum, Vltra-jectum.

[320.] Problema XXVIII. Triangulum E I O, Leida, Harlemum, Amſtelo-damum.

[321.] Problema XXIX. Triangulum I O ?, Harlemum, Amſtelodamum Alcmaria.

[322.] Problema XXX. Triangulum E O ? Leida, Amſtelodamum, Alcmaria.

[323.] Problema XXXI. Triangulum M V L, Oude-Watera, Vltrajectum, Bommelia.

[324.] Problema XXXII. Trangulum R V L, Dordracum, Trajectum, Bommelia.

[325.] Problema XXXIII. Triangulum E V L. Leida, Trajectum, Bommelia.

[326.] Problema XXXIV. Triangulum ? E L, Alcmaria, Leida, Bommelia.

[327.] Problema XXXV. Triangulum R L V. Dordracum, Bommelia, Breda.

[328.] Problema XXXVI. Triangulum R S F. Dordracum, Gouda, Rotterodamum.

[329.] Problema XXXVII. Triangulum R T F, Dordracum, Willemſtadium, Rotterodamum.

[330.] Problema XXXVIII. Triangulum R T V. Dordracum, Willemſtadium, Breda.

[331.] Problema XXXIX. Triangulum T V Q Willemſtadium, Breda, Bergaad Somum.

[332.] Problema XL. Triangulum R V Q Dordracum, Breda, Berga ad Somum.

[333.] Problema XLI. Triangulum V L Q Breda, Bommelia, Berga ad Somum.

[334.] Problema XLII. Triangulum E I ?, Leida, Harlemum, Alcmaria.

[335.] Problema XLIII. Triangulum E V ?. Leida, Trajectum, Alcmaria.

[336.] Problema XLIV. Triangulum V L ?. Trajectum, Bommelia, Alcmaria.

[337.] Problema XLV. Triangulum Q L ?. Berga ad Somum, Bommelia, Alcmaria.

[338.] Problema XLVI.

[339.] FINIS.

[340.] INTRODUCTIO AD COHÆ RENTIAM CORPORUM FIRMORUM.