Data regarding the suspended matters in these waters are extremely meagre. The official examinations of the London waters contain no records of suspended matters, although the clearness of filtered waters is daily reported. Dibden, in his analytical investigations of the London water-supply, mentioned in his book upon “The Purification of Sewage and Water,” reports the average suspended matters in the water of the Thames near the water-works intakes as 0.77 part in 100,000. No figures are available for the raw waters used by the Berlin water-works, but both are taken from lakes, and are generally quite clear. Even in times of floods of the rivers feeding the lakes, the turbidities are not very high, because the gathering grounds for the waters are almost entirely of a sandy nature, yielding waters with low turbidities, and further, the streams flow through successions of lakes before finally reaching the lakes from which the waters are taken. It is safe to assume that the suspended matters and turbidities do not exceed those of the London waters. Even at times when somewhat turbid water is obtained, due to agitation by heavy winds, the suspended matter is mainly of a sandy nature, readily removed by settling, and it does not seriously interfere with filtration. The examinations of the Massachusetts State Board of Health, with a very few exceptions, contain no statements of suspended matters. This is due to the fact that the suspended matters, in most of the waters, are so small in amount as to make them hardly capable of determination by the ordinary gravimetric processes, and the determinations if made would have but little value. The Merrimac River at Lawrence, at the time of the greatest flood in fifty years, carried silt to the amount of about 111 parts in 100,000. This was for a very short time, and the suspended matter consisted almost entirely of sand, which deposited in banks, the deposited sand having an effective size of 0.04 or 0.05 millimeter. No clayey matter is ever carried in quantity by the river. The reports of the Connecticut State Board of Health also contain no records of suspended matters for the same reason. It may be safely said that the average suspended matters of New England waters are almost always less than 1 part in 100,000. Lake waters are generally almost entirely free from sediment. At Chicago the city water drawn from Lake Michigan has slightly more than 1 part in 100,000 of suspended matters, as determined by Professor Long in 1888-9, and by Professor Palmer in 1896. The suspended matter in this case is probably due to the nearness of the intake to the mouth of the Chicago River, and to mud brought up from the bottom in times of storms. The lake-water further away from the shore would probably give much lower results.