In most if not in all Wăt there are structures known as Phra: chedi and Phra: prang. The former are simply the ancient cetiyas, called dagobas in Ceylon and zedis in Burma. They do not depart materially from the shape usual in other countries and sometimes, for instance in the gigantic chedi at Pra Pratom, the part below the spire is a solid bell-shaped dome. But Siamese taste tends to make such buildings slender and elongate and they generally consist of stone discs of decreasing size, set one on the other in a pile, which assumes in its upper parts the proportions of a flagstaff rather than of a stone building. The Phra: prangs though often larger than the Phra: chedis are proportionally thicker and less elongate. They appear to be derived from the Brahmanic temple towers of Camboja which consist of a shrine crowned by a dome. But in Siam the shrine is often at some height above the ground and is reduced to small dimensions, sometimes becoming a mere niche. In large Phra: prangs it is approached by a flight of steps outside and above it rises the tower, terminating in a metal spire. But whereas in the Phra: chedis these spires are simple, in the Phra: prangs they bear three crescents representing the trident of Śiva and appear like barbed arrows. A large Wat is sure to contain a number of these structures and may also comprise halls for preaching, a pavilion covering a model of Buddha's foot print, tanks for ablution and a bell tower. It is said that only royal Wats contain libraries and buildings called chẵtta mŭkh, which shelter a four-faced image of Brahmâ[219]. The monks are often housed in single chambers arranged round the courts of a Wat but sometimes in larger buildings outside it. The number of monks and novices living in one monastery is larger than in Burma, and according to the Bangkok Directory (1907) works out at an average of about 12. In the larger Wats this figure is considerably exceeded. Altogether there were 50,764 monks and 10,411 novices in 1907[220], the province of Ayuthia being decidedly the best provided with clergy. As in Burma, it is customary for every male to spend some time in a monastery, usually at the age of about 20, and two months is considered the minimum which is respectable. It is also common to enter a monastery for a short stay on the day when a parent is cremated. During the season of Vassa all monks go out to collect alms but at other seasons only a few make the daily round and the food collected, as in Burma and Ceylon, is generally not eaten. But during the dry season it is considered meritorious for monks to make a pilgrimage to Phra Bât and while on the way to live on charity. They engage to some extent in manual work and occupy themselves with carpentering[221]. As in Burma, education is in their hands, and they also act as doctors, though their treatment has more to do with charms and faith cures than with medicine.