CHAP. 57. (13.)—CÆRULEUM.

Cæruleum[1] is a kind of sand. In former times there were three kinds of it; the Egyptian, which was the most esteemed of all; the Scythian, which is easily dissolved, and which produces four colours when pounded, one of a lighter blue and one of a darker blue, one of a thicker consistency and one comparatively thin;[2] and the Cyprian, which is now preferred as a colour to the preceding. Since then, the kinds imported from Puteoli and Spain have been added to the list, this sand having of late been prepared there. Every kind,[3] however, is submitted to a dyeing process, it being boiled with a plant[4] used particularly for this purpose,[5] and imbibing its juices. In other respects, the mode of preparing it is similar to that of chrysocolla. From cæruleum, too, is prepared the substance known as "lomentum,"[6] it being washed and ground for the purpose. Lomentum is of a paler tint than cæruleum; the price of it is ten denarii per pound, and that of cæruleum but eight. Cæruleum is used upon a surface of clay, for upon lime it will not hold. A more recent invention is the Vestorian[7] cæruleum, so called from the person who first manufactured it: it is prepared from the finer parts of Egyptian cæruleum, and the price of it is eleven denarii per pound. That of Puteoli is used in a similar manner,[8] as also for windows:[9] it is known as "cylon."

It is not so long since that indicum[10] was first imported to Rome, the price being seventeen[11] denarii per pound. Painters make use of it for incisures, or in other words, the division of shadows from light. There is also a lomentum of very inferior quality, known to us as "ground" lomentum, and valued at only five asses per pound.

The mode of testing the genuineness of cæruleum, is to see whether it emits a flame, on being laid upon burning coals. One method of adulterating it is to boil dried violets in water, and then to strain the liquor through linen into Eretrian[12] clay.

1. "It is possible that the 'cæruleum' of the ancients may in some cases have been real ultramarine, but properly and in general, it was only copper ochre."—Beckmann's Hist. Inv. Vol. I. p. 472. Bohn's Edition. Delafosse identifies it with blue carbonate and hydrocarbonate of copper, one of the two azurites.

2. "Candidiorem nigrioremve, et crassiorem tenuioremve."

3. Beckmann thinks that Pliny is here alluding to an artificial kind of "cæruleum." "Pliny clearly adds to it an artificial colour, which in my opinion was made in the same manner as our lake; for he speaks of an earth, which when boiled with plants, acquired their blue colour."—Hist. Inv., Vol. II. p. 480.

4. Supposed by Hardouin to have been "glastum" or "woad," the Isatis tinctoria of Linnæus, mentioned in B. xxii. c. 2.

5. "In suâ coquitur herbâ."

6. A blue powder; see Chapter 27 of this Book. Beckmann has the following remarks on this and the preceding lines: "The well-known passage of Pliny in which Lehmann thinks he can with certainty discover cobalt, is so singular a medley that nothing to be depended on can be gathered from it. The author, it is true, where he treats of mineral pigments, seems to speak of a blue sand which produced different shades of blue paint, according as it was pounded coarser or finer. The palest powder was called lomentum, and this Lehmann considers as our powder-blue. I am, however, fully convinced that the cyanus of Theophrastus, the cæruleum of Pliny, and the chrysocolla (see Chapter 26), were the blue copper earth already mentioned, which may have been mixed and blended together."— Hist. Inv. Vol. I. pp. 480, 481. Bohn's Edition.

7. According to Vitruvius, B. vii. c. 11, the manufactory of Vestorius was at Puteoli, now Pozzuoli. This was probably the same C. Vestorius who was also a money-lender and a friend of Atticus, and with whom Cicero had monetary transactions. He is mentioned as "Vestorium meum," in the Epistles of Cicero to Atticus.

8. For colouring surfaces of clay or cretaceous earth. This kind was also manufactured by Vesturius, most probably.

9. "Idem et Puteolani usus, præterque ad fenestras." "The expression here, usus ad fenestras, has been misapplied by Lehmann, as a strong proof of his assertion; for he explained it as if Pliny had said that a blue pigment was used for painting window-frames; but glass windows were at that time unknown. I suspect that Pliny meant to say only that one kind of paint could not be employed near openings which afforded a passage to the light, as it soon decayed and lost its colour. This would have been the case in particular with lake, in which there was a mixture of vegetable particles."—Beckmann, Hist. Inv. Vol. I. p. 480.

10. "Indian" pigment. Probably our "indigo." It is again mentioned, and at greater length, in B. xxxv. c. 27. See also Beckmann, Hist. Inv. Vol. II. pp. 259, 267. Bohn's Edition.

11. This is probably a more correct reading than "seven."

12. See B. xxxv. c. 19. Vitruvius, B. vii. c. 14, describes an exactly similar method adopted by dyers for imitating the colour of Attic sil, or ochre, mentioned in Chapter 56.