Hourly temperatures of small streams can be accurately predicted using an energy balance. Micrometeorological measurements are required to assess the environment of the small stream accurately. The temperature-prediction technique was tested on three streams in Oregon. On unshaded stretches, net all-wave radiation is the predominant energy source during the day; evaporation and convection account for less than 10% ooe the total energy exchange. Conduction ooe heat into the stream bottom is an important energy balance component on shallow streams having a bedrock bottom. Up to 25% ooe the energy absorbed by such a stream may be transferred into the bed. Hourly temperature changes of 0-16øF were predicted to within IøF more than 90% of the time. This technique permits foresters to control water temperature through manipulation of stream-side vegetation.

The principal source of energy for warming streams is the sun. The amount of sunlight reaching the stream may be increased after clear‐cut logging. Average monthly maximum temperatures increased by 14°F and annual maximum temperatures increased from 57° to 85°F one year after clear‐cut logging on a small watershed in Oregon's coast range. In a nearby watershed where strips of brush and trees separated logging units from the stream, no changes in temperature were observed that could be attributed to clear‐ cutting.

The impact of road construction, two patterns of clear‐cut logging, and controlled slash burning on the suspended sediment yield and concentration from three small watersheds in the Oregon Coast Range was studied for 11 years. Sediment production was doubled after road construction but before logging in one watershed and was tripled after burning and clear‐cutting of another watershed. Felling and yarding did not produce statistically significant changes in sediment concentration. Variation in the relation between sediment concentration and water discharge on small undisturbed streams was large. Conclusions about the significance of all but very large changes in sediment concentration are limited because of annual variation for a given watershed, variation between watersheds, and variation with stage at a given point.

SummaryConditions for insertion of the laryngeal mask were assessed following induction of anaesthesia with either propofo12.5 rnglkg or thiopentone 4.0 mglkg in 80 patients premedicated with diazepam 10 mg. Insertion following induction with thiopentone resulted in a greater incidence of gagging ( p < 0.01). The use of additional induction agent, where necessary, resulted in no ultimate signgcant dixerence between the groups for the provision of satisfactory conditions. Key wordsAnaesthetics, intravenous; propofol, thiopentone. Equipment; laryngeal mask.The laryngeal mask is a new form of airway (LMA),' which is introduced blindly into the hypopharynx to form a seal around the larynx.2 It has been shown to provide a clear airway and leaves the anaesthetists' hands free.3 In our department the preferred induction agent for insertion of the LMA for general anaesthesia with spontaneous ventilation is propofol. In view of the relative expense of propofol and pain on injection it would be of value to confirm or disprove the advantage of this agent in this respect. MethodsThe study was approved by the District Ethics Committee. Eighty ASA 1 or 2 patients aged 18 to 70 years undergoing surgery for which the LMA was appropriate were studied. Exclusion criteria consisted of a history of asthma and any potential risk of gastric regurgitation.All patients were premedicated with diazepam 10 mg orally 2 hours before operation. Induction was with fentanyl 1 pg/kg followed by a randomly allocated equipotent dose of either propofol 2.5 mg/kg or thiopentone 4.0mg/kg, given over 30 seconds. LMA insertion, as previously described,* was by another anaesthetist who was unaware which induction agent had been given. Anaesthesia was then maintained with a volatile agent and 66% nitrous oxide in oxygen, with the patient breathing spontaneously through a Bain system. Successful atraumatic insertion requires the abolition of the gag and cough reflexes.* The anaesthetist inserting the LMA scored both reflexes using a -, + and + + system, together with any comments. The necessary use of additional induction agent was also recorded. The anaesthetists varied in experience from SHO to consultant, but all were experienced in the use of the LMA.Patients' demographic data were also noted and compared between the propofol and thiopentone groups using unpaired t-tests and a Chi-squared test. The gagging and coughing scores were compared using Mann-Whitney U tests, and the quantity of additional induction agent using a Chi-squared test and a Fisher exact probability test. Yates' correction was applied to the Chi-squared tests. A p value of < 0.05 was accepted as indicative of a significant difference.

Nutrient release from three small watersheds in Oregon's Coast Range was monitored for 2 years before and 2 years after logging. One watershed, Flynn Creek (203.14 ha), served as an untreated control. Deer Creek (303.32 ha) was patch‐cut. No change in the concentration or yield of nitrate nitrogen, phosphorus, or potassium was observed after logging. Needle Branch (70.68 ha) was clear‐cut and burned. Maximum nitrate nitrogen concentrations increased from 0.70 to 2.10 mg/1. Nitrate nitrogen concentrations returned to prelogging levels by the sixth year after logging. Yield of nitrate nitrogen increased from 4.94 to 15.66 kg/ha the first year after treatment. Potassium concentrations increased markedly after burning from about 0.60 to 4.40 mg/1 but returned to prelogging levels within 2 months. Phosphorus concentrations were unchanged. These changes pose no threat to aquatic or terrestrial productivity.